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In Vivo vs. In Vitro: What Are the Differences?

Both can advance medical knowledge but have unique limitations

• Definitions

In Vitro Medical Studies

In vivo clinical trials.

The terms "in vivo" and "in vitro" describe different types of scientific research. "In vivo" means research done on a living organism, while "in vitro" means research done in a laboratory dish or test tube.

Both types of studies are used by medical researchers developing drugs or studying diseases. Each type has benefits and drawbacks. 

In Vivo vs. In Vitro: Definitions

In vitro : The term in vitro comes from the Latin "in glass." It refers to a medical study or experiment that is done in the laboratory within the confines of a test tube or laboratory dish. This means tissue, cells, or other parts of an organism are removed and placed in a laboratory dish. Researchers may use these samples to test the action of a drug or study a disease process.

In vivo : The term in vivo comes from the Latin "in (something) living." It refers to a medical test, experiment, or procedure that is done on (or in) a living organism, such as a laboratory animal or human. 

Clinical trials or medical studies may be performed either in vivo or in vitro. These approaches are similar in that they are both done in order to make advances in the knowledge and treatment of illness and disease as well as understanding "wellness" and normal bodily functions.

But there are also many important differences in how in vivo and in vitro studies are conducted, how they can be interpreted, and the practical applications of any discoveries which are made.

Medical studies (such as looking at the ability of a drug to treat cancer) are often first performed in vitro—either in a test tube or laboratory dish. An example would be growing cancer cells  in a dish outside of the body to study them and possible treatments.

Studies are usually done in vitro first for ethical reasons. In vitro studies allow a substance to be studied safely, without subjecting humans or animals to the possible side effects or toxicity of a new drug.

Researchers learn as much as possible about a drug before exposing humans to potential negative effects. If a chemotherapy drug , for example, does not work on cancer cells grown in a dish, it would be unethical to have humans use the drug and risk the potential toxicity.

In vitro studies are important in that they allow more rapid development of new treatments—many drugs can be studied at one time (and they can be studied in a large number of samples of cells) and only those that appear to be efficacious go on to human studies.

An absence of biokinetics (how the body transports and metabolized drugs and toxins) is one of the significant drawbacks of in vitro studies. This, as well as several other factors, can make it very difficult to extrapolate the results of in vitro tests. Thus, it's hard to know what might be expected when the drug is used in vivo.

In contrast to in vitro studies, in vivo studies are needed to see how the body as a whole will respond to a particular substance.

In some cases in vitro studies of a drug will be promising, but subsequent in vivo studies fail to show any efficacy (or, on the other hand, find a drug to be unsafe) when used within the multiple metabolic processes that are continually taking place in the body.

An example of how in vivo studies are needed to evaluate drugs is with respect to drug absorption in the body. A new drug may appear to work in a dish, but not in the human body. It could be that the drug is not absorbed when it passes through the stomach, so it has little effect on humans.

In other cases, even if a drug is given intravenously , the drug might break down through continuous body reactions. Therefore, the drug would not be effective when used directly in humans.

It's important to note that oftentimes in vivo studies are first done in non-human animals such as mice. These studies allow researchers an opportunity to see how a drug works amid other bodily processes.

Mice and humans have important differences. Sometimes a drug that is effective in mice will not be effective in humans (and vice versa) due to inherent differences in the species. 

A Word From Verywell

When you look at studies done to evaluate cancer treatments—or any other treatments—checking to see which kind of study it is (in vivo vs in vitro) is an important first step.

In vitro studies are extremely important and lay the groundwork for further research, but many of these studies declare findings that are interesting—but will not affect you as an individual for quite some time to come.

In contrast, in vivo studies are looking at the actual effect on an organism—whether a laboratory animal or a human.

Saeidnia, S., Manayi, A., and M. Abdollahi. From in vitro experiments to in vivo and clinical studies; Pros and cons . Current Drug Discovery Technologies . 2015. 12(4):218-24. doi:10.2174/1570163813666160114093140

Kilkenny C, Browne W, Cuthill IC, Emerson M, Altman DG; NC3Rs Reporting Guidelines Working Group. Animal research: Reporting in vivo experiments: the ARRIVE guidelines .  Br J Pharmacol . 2010;160(7):1577–1579. doi:10.1111/j.1476-5381.2010.00872.x

By Lynne Eldridge, MD  Lynne Eldrige, MD, is a lung cancer physician, patient advocate, and award-winning author of "Avoiding Cancer One Day at a Time."

Science-Based Medicine

Exploring issues and controversies in the relationship between science and medicine

Ethics in human experimentation in science-based medicine

Science-based medicine depends upon human experimentation. Scientists can do the most fantastic translational research in the world, starting with elegant hypotheses, tested through in vitro and biochemical experiments, after which they are tested in animals. They can understand disease mechanisms to the individual amino acid level in a protein or nucleotide in a DNA molecule. However, without human testing, they will never know if the end results of all that elegant science will actually do what it is intended to do and to make real human patients better. They will never know if the fruits of all that labor will actually cure disease. However, it is in human experimentation where the ethics of science most tend to clash with the mechanisms of science. We refer to “science-based medicine” ( SBM ) as “based” in science, but not science, largely because medicine can never be pure science. Science has resulted in amazing medical advances over the last century, but if there is one thing that we have learned it’s that, because clinical trials involve living, breathing, fellow human beings, what is the most scientifically rigorous trial design might not be the most ethical.

About a week ago, the AP reported that experiments and clinical trials that resemble the infamous Tuskegee syphilis study and the less well known, but recently revealed Guatemala syphilis experiment were far more common than we might like to admit. As I sat through talks about clinical trial results at the Society of Surgical Oncology meeting in San Antonio over the weekend, the revelations of the last week reminded me that the intersection between science and ethics in medicine can frequently be a very tough question indeed. In fact, in many of the discussions, questions of what could or could not be done based on ethics were frequently mentioned, such as whether it is ethically acceptable or possible to do certain followup trials to famous breast cancer clinical trials. Unfortunately, it was not so long ago that such questions were answered in ways that bring shame on the medical profession.

More than Tuskegee and Guatemala

The most notorious of highly unethical human experiments outside of Nazi Germany and the Japanese empire during World War II is the infamous Tuskegee syphilis study . This study, conducted by our very own Public Health Service (PHS) was conducted between 1932 and 1972 and examined the natural progression of untreated syphilis in poor black men who received free health care from the government. In 1932, when this study was conceived it was not inherently unethical. At the time there were precious few treatments for syphilis, and none of them worked very well. Consequently, observing the progression of syphilis, using the treatments available at the time, and following the subjects prospectively constituted a reasonable trial design. However, in the late 1930s and early 1940s, penicillin became available, and by 1947 was the standard of care for treating syphilis. When campaigns to eradicate syphilis came to the county in which most of the subjects, study researchers prevented their subjects from participating. In essence, even after an effective treatment for syphilis had become widely available, study still researchers denied it to their subjects. By the end of the study in 1972, of the original 399 men in the study, 28 had died of syphilis; 100 were dead of related complications; 40 wives had been infected with syphilis; and 19 children had been born with congenital syphilis. The rationale for not providing effective treatment for these men and even discouraging them from undergoing such treatment? This :

Such individuals seemed to offer an unusual opportunity to study the untreated syphilitic patients from the beginning of the disease to the death of the infected person. An opportunity was also offered to compare the syphilitc process uninfluenced by modern treatment, with the results attained when treatment had been given.

Worse, there was no informed consent, and considerable inducements were offered to the men to join the study.

The Tuskegee syphilis study, unfortunately, is not the only abuse committed by the PHS. About six months ago, it was revealed that these sorts of experiments had been more widespread than commonly believed. Indeed, in the 1940s in Guatemala, the PHS had gone one better in that they had deliberately infected prison inmates in Guatemala with syphilis. As I described in a lot more detail when the revelations first hit the press, prostitutes who had tested positive for syphilis were recruited to visit the men in prison. The hypothesis to be tested was whether prophylactic penicillin treatment could prevent infection, and the other purpose was to define the response of syphilis to penicillin treatment. Again, there was no real informed consent. Worse, subjects were intentionally infected with a potentially fatal disease. True, they were treated, but treatment is not 100% effective, and one has to wonder if the prisoners, a vulnerable population, understood the nature of the risks they were being induced to take.

On Sunday, AP medical writer Michael Stobbe published a long article detailing the sordid history of medical research in the U.S. before the 1970s. His timing was not coincidental, because on Tuesday in Washington, DC, there was a meeting of a presidential bioethics committee, the Commission for the Study of Bioethical Issues, triggered by the revelations last fall about the Guatemala syphilis experiment 65 years ago. Those revelations led the AP to do an exhaustive review of reports from medical journals and press clippings, and the AP found at least 40 studies similar to the Guatemala syphilis study in that patients were put at risk for serious disease or, even worse, healthy people were intentionally made ill to study disease. Some of these abuses are well known, others much less so.

Here are some examples from the AP article:

The AP review of past research found: A federally funded study begun in 1942 injected experimental flu vaccine in male patients at a state insane asylum in Ypsilanti, Mich., then exposed them to flu several months later. It was co-authored by Dr. Jonas Salk, who a decade later would become famous as inventor of the polio vaccine. Some of the men weren’t able to describe their symptoms, raising serious questions about how well they understood what was being done to them. One newspaper account mentioned the test subjects were “senile and debilitated.” Then it quickly moved on to the promising results. In federally funded studies in the 1940s, noted researcher Dr. W. Paul Havens Jr. exposed men to hepatitis in a series of experiments, including one using patients from mental institutions in Middletown and Norwich, Conn. Havens, a World Health Organization expert on viral diseases, was one of the first scientists to differentiate types of hepatitis and their causes. A search of various news archives found no mention of the mental patients study, which made eight healthy men ill but broke no new ground in understanding the disease. Researchers in the mid-1940s studied the transmission of a deadly stomach bug by having young men swallow unfiltered stool suspension. The study was conducted at the New York State Vocational Institution, a reformatory prison in West Coxsackie. The point was to see how well the disease spread that way as compared to spraying the germs and having test subjects breathe it. Swallowing it was a more effective way to spread the disease, the researchers concluded. The study doesn’t explain if the men were rewarded for this awful task. A University of Minnesota study in the late 1940s injected 11 public service employee volunteers with malaria, then starved them for five days. Some were also subjected to hard labor, and those men lost an average of 14 pounds. They were treated for malarial fevers with quinine sulfate. One of the authors was Ancel Keys, a noted dietary scientist who developed K-rations for the military and the Mediterranean diet for the public. But a search of various news archives found no mention of the study. For a study in 1957, when the Asian flu pandemic was spreading, federal researchers sprayed the virus in the noses of 23 inmates at Patuxent prison in Jessup, Md., to compare their reactions to those of 32 virus-exposed inmates who had been given a new vaccine. Government researchers in the 1950s tried to infect about two dozen volunteering prison inmates with gonorrhea using two different methods in an experiment at a federal penitentiary in Atlanta. The bacteria was pumped directly into the urinary tract through the penis, according to their paper. The men quickly developed the disease, but the researchers noted this method wasn’t comparable to how men normally got infected — by having sex with an infected partner. The men were later treated with antibiotics. The study was published in the Journal of the American Medical Association , but there was no mention of it in various news archives.

Stobbe goes on to point out the “Holy Trinity” of news stories in the 1960s and early 1970s that brought to light the sorts of activities that we now consider abuses in medical research. The last of these was, of course, the Tuskegee syphilis study. The first of these occurred in 1963, when it came to light that researchers had injected cancer cells into elderly debilitated patients at the Jewish Chronic Disease Hospital in Brooklyn to discover whether their bodies would reject them. With our knowledge of tumor immunology now, we can look back on this experiment and know that the odds of any harm were quite small because tumors, with very, very rare exceptions, are not transplantable in humans. Our bodies recognize cells from another person to be foreign, whether they are cancer or not, and quickly destroy them. However, at the time, based on what was known, undoubtedly the scientists thought that there was at least a chance that these tumor cells would form cancers in the patients into whom they were injected, the denial of the hospital director who deemed the cells “harmless,” notwithstanding. (Indeed, the hospital director strikes me as either lying or deluded.) Otherwise, why seek to answer the question? Just as bad, there was no informed consent, the justification being that the cells were thought to be “harmless.” More details can be found here . The outcome was that the Board of Regents censured the researchers and suspended the licenses of two of the doctors involved. Later, however, they stayed the suspensions and instead put the doctors on probation for one year. There were no repercussions for the hospital or for Memorial Sloan-Kettering Cancer Center, where one of the investigators was on faculty.

The third of the “Holy Trinity” was an infamous experiment in Staten Island at the Willowbrook State School, which was a school for children with mental retardation. During the mid-1960s, children there were intentionally infected with hepatitis in order to determine whether gamma globulin could cure it. Besides the targeting of a vulnerable population (children and teens with profound mental retardation), this study demonstrated a number of problematic issues as well . First, the investigators rationalized infecting these children by rationalizing that hepatitis was so endemic in the facility due to the fact that most of the children there were incapable of being toilet trained that over 70% of new residents became infected within a year. This, of course, leads to the obvious question , namely: If that were the case then why not study the effect of gamma globulin on children who were infected normally? More disturbing, again investigators played fast and loose with informed consent, the form being worded in a vague and ambiguous manner that played down the fact that the children were going to be intentionally infected with hepatitis and implying that the serum they would be given would be an experimental vaccine. Finally, as is the case in many such studies, there was an element of coercion. Willowbrook at the time was very crowded, with long waiting lists for children to be admitted. At times, there was only room in the experimental wing. For parents who could not afford to take care of their children, this situation could bring considerable pressure to bear to “persuade” them to “do the right thing.”

Changing ethics

In studying the history of medicine and clinical trials, what never ceases to amaze me is the different attitudes that physicians and scientists had towards their human subjects not all that long ago. Remember, it was primarily in the 1960s and 1970s when attitudes began to change. Before the 1970s, for instance, researchers thought little of using prisoners for experiments, even though prisoners are correctly considered a population that is vulnerable and for whom true informed consent without coercion is difficult to obtain without special attention to making it happen. Indeed, in his news story Stobbe recounts an anecdote of a man at Holmesburg Prison in Philadelphia who agreed in exchange for cigarette money to have the skin peeled off of his back and searing chemicals painted on the open wounds in order to test a drug. Similarly, as the Willowbrook story shows us, it was not really all that long ago when scientists apparently felt justified in infecting profoundly mentally retarded children with hepatitis on the basis of at best dubious ethical justification.

Arguably, this willingness to experiment on children who were not normal and who were never going to be able to contribute to society was a holdover from the eugenics movement earlier in the 20th century. It’s important to remember that, however much eugenics was discredited by the Nazis, prior to the Holocaust Hitler was actually quite the admirer of American eugenics policies, drawing inspiration from them. Another factor that is frequently invoked as an explanation for the willingness of American scientists to flout ethical considerations is war, particularly World War II and then the Cold War, the resulting idea that it was “us against them,” and that for us to win would require shared sacrifice in the name of the nation. After all, the scientific primacy of the U.S. was viewed as one of the most critical sources of our economic and military strength. Moreover, the concept of the Cold War could be generalized to other “wars,” such as the “war on disease” or the current “war on cancer” that I’ve written about twice in the last month. As Stobbe put it:

Attitudes about medical research were different then. Infectious diseases killed many more people years ago, and doctors worked urgently to invent and test cures. Many prominent researchers felt it was legitimate to experiment on people who did not have full rights in society — people like prisoners, mental patients, poor blacks. It was an attitude in some ways similar to that of Nazi doctors experimenting on Jews. “There was definitely a sense — that we don’t have today — that sacrifice for the nation was important,” said Laura Stark, a Wesleyan University assistant professor of science in society, who is writing a book about past federal medical experiments.

There was clearly also more than a little hubris at play as well:

It was at about this time that prosecution of Nazi doctors in 1947 led to the “Nuremberg Code,” a set of international rules to protect human test subjects. Many U.S. doctors essentially ignored them, arguing that they applied to Nazi atrocities — not to American medicine.

Finally, with the rise of large pharmaceutical companies in the 1940s and 1950s, increasingly there was more of a profit motive than a purely scientific one. Drugs needed to be tested, and prisoners provided a convenient source of young, healthy men upon which to test new products. Hubris, profit, and a wartime attitude that sacrificing for the good of the nation all swirled together into a mixture toxic to medical ethics during World War II and well into the postwar period. In having defeated the Nazis, we failed to learn a lesson from what had happened in Germany, where one of the most technologically and medically advanced societies then on the face of the earth did horrible things in the name of its ideology.

Yes, it is true that American scientists did not intentionally expose prisoners to freezing water in experiments designed to find better ways of rewarming pilots shot down over frigid waters or sailors who survived the sinking of their ship, as Nazi doctors did. It is also true that American scientists did not intentionally irradiate men’s testicles and women’s ovaries in order to develop a means of rapid sterilization, causing horrific bowel and bladder complications, especially in women, as Nazi scientists did, although American scientists did subject many to various radioactive substances in the name of research. Nor did American scientists inject dyes into the eyes of children in order to try to turn them blue, as Dr. Mengele did. On the other hand, American scientists did, as we have seen, intentionally infect prisoners and mentally retarded children (the same sort of children that the Nazis would have called “life unworthy of life”) with diseases and then treat them, just as Nazi physicians intentionally infected concentration camp inmates with various diseases in order to determine the efficacy of different treatments or as Japanese physicians did when they intentionally broke the limbs of prisoners and contaminated them with bacteria-laden dirt. American offenses were different in scale and horror, but not significantly different in kind. Unfortunately, it was not until the 1970s, years after the international Helsinki Declaration was first published, until the Belmont Report was adopted and then not until the 1990s when The Common Rule became the basis of all federal regulations protecting human research subjects, as I have described before .

Could it happen again?

Fortunately, as one who now participates in clinical trials and clinical trial development, given the current level of regulation on human subjects research by the federal government, I have a hard time imagining how abuses such as the one’s I’ve described could happen again now. The amount of paperwork, regulation, and oversight of clinical trials has become so burdensome and complex that sometimes I wonder why I or anyone else would want to continue doing clinical research. Unfortunately, Stobbe doesn’t sound too optimistic. Actually, it’s not so much Stobbe, but rather the presidential Commission for the Study of Bioethical Issues, as Stobbe documents in a followup story :

Speakers noted that over the last several decades, as many as 1,000 rules, regulations and guidelines have been enacted worldwide to ensure the ethical conduct of medical research. In the United States, there are rules to protect people in every study done by federal scientists, funded by federal agencies or those testing a product requiring federal approval to be sold. But that oversight is inconsistent — ethical rules can vary among federal agencies. What’s more, if federal funding or review is not involved, an unethical study could be done and no one in authority would ever know about it. “We have a leaky system,” said Eric Meslin, director of the Indiana University Center for Bioethics. Dr. Robert Califf, Duke University’s vice chancellor for clinical research, agreed there are weaknesses. “It’s night and day and what you could do in the ‘good old days’ with no one knowing about it. But there’s no 100 percent guarantee. There still will be bad things that will happen,” he said.

In terms of pharmaceutical companies, there are clearly loopholes when it comes to overseas studies. Indeed, pharmaceutical companies have been doing more and more studies overseas. Although federal law states that such studies, if they are funded by the federal government or if they are to be used as part of an application for FDA approval of a drug, that is not always enough of a guarantee of oversight :

Last year, the U.S. Department of Health and Human Services’ inspector general reported that between 40 and 65 percent of clinical studies of federally regulated medical products were done in other countries in 2008, and that proportion probably has grown. The report also noted that U.S. regulators inspected fewer than 1 percent of foreign clinical trial sites.

Clearly, this is an unacceptable level of oversight, particularly outside of developed countries, such as those in Europe, where clinical trial oversight is comparable to that in the U.S.

Ironically, two examples come to mind of clinical trials that show the holes in our regulatory system for human subjects protection, both of which I have written about right here on SBM before. The first trial was a trial of homeopathic remedies for infants with infectious diarrhea in Honduras, as I wrote about here and Wally Sampson wrote about here . At the time I couldn’t figure out how the investigators at the University of Washington managed to get this study through their IRB, but somehow they did, demonstrating that an IRB is not a guarantee against the approval of totally unethical and scientifically worthless experiments. Fortunately, as far as I can tell, no infant was injured, but the potential was definitely there. Then, let’s not forget the Gonzalez trial, a trial of a regimen of what can best be described as pure quackery consisting of up to 150 supplement pills a day, various nutritional pseudoscience, and daily (or more) coffee enemas. The results were devastating , in that subjects on the standard-of-care chemotherapy arm lived three times longer than those on the Gonzalez protocol arm. Such is the effect of the National Center for Complementary and Alternative Medicine ( NCCAM ) on research ethics.

The more disturbing example is Mark and David Geier, the father-son tag team of anti-vaccine activists who fervently believe that mercury in vaccines causes autism and somehow came up with an idea that can only be described as dangerously wacky, namely that by suppressing testosterone with a powerful drug (Lupron) they could make the quackery known as chelation therapy “work better” at chelating mercury from the brains of autistic children. The reason? Because “testosterone sheets” bind mercury and keep it from being chelated! In pursuing this research, the Geiers have created an IRB stocked with their cronies and fellow anti-vaccinationists to “oversee” the research, as Kathleen Seidel has so thoroughly documented . In the process, autistic children were subjected to a powerful drug that depresses their sex hormone levels, which is why its use is often referred to as “chemical castration.” Predictably, Anne Dachel, Media Editor over at the anti-vaccine crank blog Age of Autism, has leapt all over this story as “evidence” that vaccines must be dangerous and that unethical scientists have been lying all along about the science showing tthat there is no evidence that vaccines cause autism:

Either Stobbe is a naïve and trusting soul and can’t consider that the same government that allowed horrific medical experiments in the past also allowed our children to become vaccine guinea pigs, or he’s afraid of an issue that’s just too controversial to talk about here and now. It’s much safer to attack what went on in the last century. Maybe 70 years from now, some enterprising reporter will bring up the ethics of injecting known neurotoxins in pregnant women, babies, and small children. Maybe around 2080, they’ll ask why no one ever demanded independent studies on the cumulative effect of so many vaccines, so soon, on the health of a baby. Or why there was never a simple vax-nonvax comparison study looking at autism rates.

Or maybe in 2050, Dachel will understand that this is the sort of work that’s been replicated so many times and done in so many different countries that even if you were to throw out all the U.S. data it wouldn’t change the conclusion that vaccines do not cause autism. She also overlooks the fact that the vast majority of the studies that have failed to find a link between vaccines and autism were performed after the adoption of the Common Rule and much-increased federal oversight over clinical trials. Of course, stories like Stobbe’s make it easier for cranks to attack the entire U.S. clinical research enterprise as corrupt and unethical. However, that is not the reason why we need to close the loopholes in our current clinical trial regulations. We need to do it because it is the right thing to do.

We at SBM argue that medicine should be based on science, rather than be a science, because we realize that medicine can never be completely scientific. There are too many human variables, not the least of which are patient values, individual patient situations, and resources. Another reason is the clinical trial process itself. Sometimes the most scientifically rigorous clinical trial design is not the most ethical design; indeed, sometimes it might be downright unethical. One example is, as I have pointed out , the aforementioned study of vaccinated versus unvaccinated children that seems to be every anti-vaccine activist’s most fervent dream. The most scientifically rigorous design for such a study would be a randomized, double-blind, placebo-controlled trial. However, such a trial would leave half of its participants completely unprotected against potentially deadly childhood infectious diseases, making it totally unethical to perform, even if it could be scientifically and fiscally justified based on existing preliminary data, which it really cannot.

Perhaps a better example is how placebo-controlled trials have almost gone the way of the dodo in cancer chemotherapy trials. Most oncology trials are now designed to test a new drug against the current standard of care or the new drug plus the standard of care versus standard of care alone. This is because our ethical considerations have evolved such that we now no longer consider giving placebos to cancer patients to be ethical unless there truly is no existing effective treatment for their cancer or if we truly do not know if the proposed treatment is better than observation alone and observation alone is currently the standard of care. As I have described before, in clinical trials, there must be clinical equipoise ; i.e., based on the scientific evidence as it is known at the time the trial begins, a reasonable scientific assessment of the risks and benefits must conclude that the risks to the experimental group are either minimal or outweighed by the potential benefits. Here’s another thought to chew on. Experiments in which people were intentionally exposed to infectious agents and then subjected to various treatments to cure the disease thus caused are potentially the most scientifically rigorous way of all to test such treatments in humans because they allow control of the start of the infection, the amount of bacteria injected, and many other variables that can’t be so easily controlled in “wild” cases of infectious disease. However, because such experiments violate the precept of, “First, do no harm,” they are utterly unethical and now properly condemned by any physician with a shred of ethics. That we should require laws, rules, and regulations to prevent such unethical experiments by scientists is unfortunately, but scientists are no different than any other person. Not all of them are ethical; some are completely unethical. Some can be corrupted.

There will always be unethical scientists, at least as long as there are unethical people. That’s why we need laws to protect human subjects. However, we must also remember that the protection of human subjects is a balancing act. Go too far in the direction of lax regulation, and incidents such as those described in Stobbe’s article will start to happen again. Go too far in the other direction, and the pace of discovery will grind to a halt. Key to finding the balance is to respect patient autonomy and to provide true informed consent that accurately balances risks versus benefits and to protect patients from any form of coercion. Doing so without making the clinical trial process so onerous that researchers flee the field while at the same time protecting patients from foreseeable harms will be the challenge.

Dr. Gorski's full information can be found here , along with information for patients. David H. Gorski, MD, PhD, FACS is a surgical oncologist at the Barbara Ann Karmanos Cancer Institute specializing in breast cancer surgery, where he also serves as the American College of Surgeons Committee on Cancer Liaison Physician as well as an Associate Professor of Surgery and member of the faculty of the Graduate Program in Cancer Biology at Wayne State University. If you are a potential patient and found this page through a Google search, please check out Dr. Gorski's biographical information, disclaimers regarding his writings, and notice to patients here .

• Posted in: Clinical Trials , Medical Ethics , Pharmaceuticals , Science and the Media

Posted by David Gorski

Nuremberg Code

The Nuremberg Military Tribunal’s decision in the case of the United States v Karl Brandt et al. includes what is now called the Nuremberg Code, a ten point statement delimiting permissible medical experimentation on human subjects. According to this statement, humane experimentation is justified only if its results benefit society and it is carried out in accord with basic principles that “satisfy moral, ethical, and legal concepts.”

—“Permissible Medical Experiments.” Trials of War Criminals before the Nuremberg Military Tribunals under Control Council Law No. 10. Nuremberg October 1946 – April 1949, Washington. U.S. Government Printing Office (n.d.), vol. 2., pp. 181-182.

The voluntary consent of the human subject is absolutely essential. This means that the person involved should have legal capacity to give consent; should be situated as to be able to exercise free power of choice, without the intervention of any element of force, fraud, deceit, duress, over-reaching, or other ulterior form of constraint or coercion, and should have sufficient knowledge and comprehension of the elements of the subject matter involved as to enable him to make an understanding and enlightened decision. This latter element requires that before the acceptance of an affirmative decision by the experimental subject there should be made known to him the nature, duration, and purpose of the experiment; the method and means by which it is to be conducted; all inconveniences and hazards reasonably to be expected; and the effects upon his health or person which may possibly come from his participation in the experiment.

The duty and responsibility for ascertaining the quality of the consent rests upon each individual who initiates, directs or engages in the experiment. It is a personal duty and responsibility which may not be delegated to another with impunity.

• The experiment should be such as to yield fruitful results for the good of society, unprocurable by other methods or means of study, and not random and unnecessary in nature.
• The experiment should be so designed and based on the results of animal experimentation and a knowledge of the natural history of the disease or other problem under study that the anticipated results will justify the performance of the experiment.
• The experiment should be so conducted as to avoid all unnecessary physical and mental suffering and injury.
• No experiment should be conducted where there is an a priori reason to believe that death or disabling injury will occur; except, perhaps, in those experiments where the experimental physicians also serve as subjects.
• The degree of risk to be taken should never exceed that determined by the humanitarian importance of the problem to be solved by the experiment.
• Proper preparations should be made and adequate facilities provided to protect the experimental subject against even remote possibilities of injury disability or death.
• The experiment should be conducted only by scientifically qualified persons. The highest degree of skill and care should be required through all stages of the experiment of those who conduct or engage in the experiment.
• During the course of the experiment the human subject should be at liberty to bring the experiment to an end if he has reached the physical or mental state where continuation of the experiment seems to him to be impossible.
• During the course of the experiment the scientist in charge must be prepared to terminate the experiment at any stage, if he has probable cause to believe, in the exercise of the good faith, superior skill and careful judgement required by him that a continuation of the experiment is likely to result in injury, disability, or death to the experimental subject.

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Innovative therapy may appear to coincide with medical experimentation, raising ethical and legal issues, for instance on informed consent and institutional review. Medical treatments may be classified, however, to distinquish novel procedures from experimentation.

• Copyright © 1975 by Canadian Medical Association

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Clinical Research: Benefits, Risks, and Safety

On this page:

What are the potential benefits of participating in clinical research?

What are the potential risks of participating in clinical research, will i always get the experimental treatment in a clinical trial, how is the safety of clinical research participants protected.

If you’re interested in volunteering for clinical research, you may wonder: What makes a study a good fit for me? How do I know it’s safe? Clinical research involves studying health and illness in people through observational studies or clinical trials . Participating in a trial or study has many potential benefits and also some possible risks. Learn about the benefits and risks of participating in clinical research and how your safety is protected.

There are many possible benefits of being part of clinical research, including:

• You may have the chance to help scientists better understand your disease or condition and to advance treatments and ways to prevent it in the future.
• You may feel like you’re playing a more active role in your health.
• You may learn more about your disease or condition.
• You may be able to get information about support groups and resources.

In addition, some people participate in clinical trials because they hope to gain access to a potential new treatment for a disease before it is widely available.

Clinical trials and studies do come with some possible risks, including:

• The research may involve tests that pose a risk to participants. For example, certain physical tests may increase the chance of falling, and X-rays may cause a small increase in the risk of developing cancer.
• Participating in a study could also be inconvenient for you. For example, you may be required to have additional or longer medical appointments, more procedures, complex medication instructions, or hospital stays.

Additional risks of participating in clinical trials may include:

• For those who receive the experimental treatment, it may be uncomfortable or cause side effects (which can range from mild to serious).
• The experimental treatment might not work, or it may not be better than the standard treatment.
• For trials testing a new treatment, such as a new medication or device, you may end up not being part of the group that gets the experimental treatment. Instead, you may be assigned to the control (or comparison) group. In some studies, the control group receives a placebo, which is given in the same way as the treatment but has no effect.

Participant confidentiality is a concern in any kind of research. People other than the researchers, such as the study sponsors or experts who monitor safety, may be able to access medical information related to the study. Safeguards are in place to ensure that researchers tell potential participants what information could be shared and how their privacy will be protected before they consent to participate in research.

The study coordinators will provide detailed information and answer questions about the risks and benefits of participating in a particular study. Having this information can help you make an informed decision about whether to participate.

Clinical trial volunteers do not always get the treatment being tested. The gold standard for testing interventions in people is called a randomized controlled trial. Randomized means that volunteers are randomly assigned — chosen by chance — to receive either the experimental intervention (the test group) or a placebo or the current standard care (the control or comparison group). Then, researchers compare the effects in each group to determine whether the new treatment works.

When you enroll in a clinical trial, you may be assigned to the test group or to the control group. While participants in the control group do not receive the experimental treatment, these volunteers are just as important as those in the test group. Without the control group, scientists cannot be sure whether an experimental treatment is better than the standard or no treatment.

In many cases, you won’t know until the end of the trial whether you are in the test group or the control group. That’s because knowing the group assignment might influence the results of the trial. Studies are often “blinded” (or “masked”) to prevent this accidental bias. In a single-blind study, you are not told whether you are in the test group or the control group, but the research team knows. In a double-blind study, neither you nor the research team knows what group you are in until the trial is over. If medically necessary, however, it is always possible to find out which group you are in.

What is a placebo?

Whenever possible, clinical trials compare a new treatment for a specific condition to the standard treatment for that condition. When there is no standard treatment available, scientists may compare the new treatment to a placebo, which looks like the drug or treatment being tested but isn’t meant to actually change anything in your body. A pill that doesn’t contain any medicine is one example.

A trial that uses a placebo is described as a “placebo-controlled trial.” In this type of study, the test group receives the experimental treatment, and the control group receives the placebo.

Placebos are not used if an effective treatment is already available or if you would be put at risk by not having effective therapy. You will be told if placebos are used in the study before entering a trial as part of the process of informed consent.

What happens if a clinical trial ends early?

Most clinical trials run as planned from beginning to end. However, sometimes researchers end trials early. Clinical trials may be paused or stopped for a number of reasons:

• There is clear evidence that one intervention is more effective than another. When this happens, the trial may be stopped so that the new treatment can be made available to other people as soon as possible.
• The trial shows that the treatment doesn’t work or causes unexpected and serious side effects.
• The researchers can’t enroll enough people in the trial to provide meaningful results.

Even when a clinical trial ends early, it can still provide researchers with valuable information. For example, scientists may gain insights about how to best design and conduct clinical trials in a specific research area. In some cases, health information collected during a trial can lead to new potential therapies that researchers can test in the future.

Based on many years of experience and learning from past mistakes, strict rules are in place to keep participants safe . Today, every clinical investigator in the United States is required to monitor and make sure that every participant is safe. These safeguards are an essential part of the research.

Each clinical study follows a careful study plan, called a protocol, which describes what the researchers will do. The principal investigator, or head researcher, is responsible for ensuring the protocol is followed.

Safeguards to protect clinical research volunteers include Institutional Review Boards, informed consent, Data and Safety Monitoring Boards, and Observational Study Monitoring Boards.

• Most clinical studies in the U.S. must be approved by an Institutional Review Board (IRB) . The IRB is made up of doctors, scientists, and members of the general public who ensure that the study participants are not exposed to unnecessary risks. The people on the IRB regularly review the study and its results. They make sure that risks (or potential harm) to participants do not outweigh the potential benefits of the study.
• Informed consent also helps protect participants. Informed consent is the process by which you learn the key facts about a study before deciding whether to participate. Members of the research team explain the research before you start and throughout the study. They provide an informed consent document, which includes details about the study, such as its purpose, how long it will last, required procedures, and who to contact. The informed consent document also explains risks and potential benefits. You are free to ask questions, request more information, or withdraw from the study at any time.

Clinical trials and studies also have committees that monitor the safety of the research as it occurs.

• Clinical trials that test an intervention are closely supervised by a Data and Safety Monitoring Board . The board is made up of experts who review the results of the study as it progresses. If they determine that the experimental treatment is not working or is harming participants, they can stop the trial early.
• Observational Study Monitoring Boards monitor the safety of observational studies with large or vulnerable populations, or risks associated with tests or standard of care.

Several historical incidents have caused mistrust in clinical research. These events also led to the creation of laws that provide clinical research participants with multiple levels of protection.

One example is the U.S. Public Health Service Syphilis Study at Tuskegee , which was conducted between 1932 and 1972. In this study, researchers wanted to determine the effects of untreated syphilis. They did not explain the study’s risks or obtain informed consent from the participants, all of whom were Black men. They also did not offer the study participants penicillin when it became widely available in the mid-1940s, causing preventable illness and suffering. After news of the study leaked in 1972, it led to sweeping changes in standard research practices and guidelines to protect human research participants. Today, IRBs are responsible for reviewing all studies involving humans to ensure they meet these guidelines and for reporting any study plan that breaks the rules.

After obtaining all the information, you can make an informed decision about whether or not to participate in a clinical trial or study. If you decide to volunteer for clinical research, you will be given an informed consent form to sign. By signing the form, you show that you understand the details and want to be part of the research. However, the informed consent form is not a contract. You may leave the study at any time and for any reason.

Where can I find a clinical trial or study?

Looking for clinical research related to aging and age-related health conditions? There are many ways to find a trial or study. Talk to your health care provider and use online resources to:

• Search for a clinical trial or study .
• Look for clinical trials on Alzheimer’s disease, other dementias, and caregiving .
• Find a registry for a particular diagnosis or condition .
• Explore clinical trials and studies funded by NIA .

To learn more about a particular trial or study, you or your doctor can contact the research staff and ask questions. You can usually find contact information in the study description.

You may also be interested in

• Getting more information about clinical trials and studies
• Downloading and sharing an infographic with the benefits of participating in clinical research
• Learning about participating in Alzheimer's disease research

For more information about clinical research

Clinical Research Trials and You National Institutes of Health www.nih.gov/health-information/nih-clinical-research-trials-you

ClinicalTrials.gov www.clinicaltrials.gov 

U.S. Food and Drug Administration 888-463-6332 [email protected] www.fda.gov

This content is provided by the NIH National Institute on Aging (NIA). NIA scientists and other experts review this content to ensure it is accurate and up to date.

Content reviewed: May 18, 2023

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Medical experimentation on humans: a moral point of view

Affiliation.

• 1 Department of Nursing, Tel Aviv University, Ramat Aviv, Israel.
• PMID: 1484460

This article deals with the medical ethical dilemma in performing experiments on humans. Its aim is to examine and offer solutions to the complex subject of medical experimentation in relation to the medical community, society, the patient, doctor and nurse, keeping in mind the importance of its benefits to the patient and to medical research. Doctors are obliged to follow the rules dictated by medical ethics, and are guided by them in times of decision-making and judgments regarding the performance of medical experimentation.

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• Beyond voluntary consent: Hans Jonas on the moral requirements of human experimentation. Fethe C. Fethe C. J Med Ethics. 1993 Jun;19(2):99-103. doi: 10.1136/jme.19.2.99. J Med Ethics. 1993. PMID: 8331645 Free PMC article.
• How important is consent for controlled clinical trials? MacKinnon B. MacKinnon B. Camb Q Healthc Ethics. 1996 Spring;5(2):221-7. doi: 10.1017/s0963180100006964. Camb Q Healthc Ethics. 1996. PMID: 8718728 Review. No abstract available.
• No-fault compensation for human subjects injured in biomedical research: a public policy conflict. Glass JC. Glass JC. Pharos Alpha Omega Alpha Honor Med Soc. 1985 Summer;48(3):2-7. Pharos Alpha Omega Alpha Honor Med Soc. 1985. PMID: 4034661 No abstract available.
• Biomedical experimentation on the mentally handicapped: ethical and legal dilemmas. Baudouin JL. Baudouin JL. Med Law. 1990;9(4):1052-61. Med Law. 1990. PMID: 2125103 Review.
• Human experimentation. Protecting patient autonomy through informed consent. Tuthill KA. Tuthill KA. J Leg Med. 1997 Jun;18(2):221-50. doi: 10.1080/01947649709511033. J Leg Med. 1997. PMID: 9230568 Review. No abstract available.
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Methodology

• Guide to Experimental Design | Overview, Steps, & Examples

Guide to Experimental Design | Overview, 5 steps & Examples

Published on December 3, 2019 by Rebecca Bevans . Revised on June 21, 2023.

Experiments are used to study causal relationships . You manipulate one or more independent variables and measure their effect on one or more dependent variables.

Experimental design create a set of procedures to systematically test a hypothesis . A good experimental design requires a strong understanding of the system you are studying.

There are five key steps in designing an experiment:

• Consider your variables and how they are related
• Write a specific, testable hypothesis
• Design experimental treatments to manipulate your independent variable
• Assign subjects to groups, either between-subjects or within-subjects
• Plan how you will measure your dependent variable

For valid conclusions, you also need to select a representative sample and control any  extraneous variables that might influence your results. If random assignment of participants to control and treatment groups is impossible, unethical, or highly difficult, consider an observational study instead. This minimizes several types of research bias, particularly sampling bias , survivorship bias , and attrition bias as time passes.

Table of contents

Step 1: define your variables, step 2: write your hypothesis, step 3: design your experimental treatments, step 4: assign your subjects to treatment groups, step 5: measure your dependent variable, other interesting articles, frequently asked questions about experiments.

You should begin with a specific research question . We will work with two research question examples, one from health sciences and one from ecology:

To translate your research question into an experimental hypothesis, you need to define the main variables and make predictions about how they are related.

Start by simply listing the independent and dependent variables .

Then you need to think about possible extraneous and confounding variables and consider how you might control  them in your experiment.

Finally, you can put these variables together into a diagram. Use arrows to show the possible relationships between variables and include signs to show the expected direction of the relationships.

Here we predict that increasing temperature will increase soil respiration and decrease soil moisture, while decreasing soil moisture will lead to decreased soil respiration.

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Now that you have a strong conceptual understanding of the system you are studying, you should be able to write a specific, testable hypothesis that addresses your research question.

The next steps will describe how to design a controlled experiment . In a controlled experiment, you must be able to:

• Systematically and precisely manipulate the independent variable(s).
• Precisely measure the dependent variable(s).
• Control any potential confounding variables.

If your study system doesn’t match these criteria, there are other types of research you can use to answer your research question.

How you manipulate the independent variable can affect the experiment’s external validity – that is, the extent to which the results can be generalized and applied to the broader world.

First, you may need to decide how widely to vary your independent variable.

• just slightly above the natural range for your study region.
• over a wider range of temperatures to mimic future warming.
• over an extreme range that is beyond any possible natural variation.

Second, you may need to choose how finely to vary your independent variable. Sometimes this choice is made for you by your experimental system, but often you will need to decide, and this will affect how much you can infer from your results.

• a categorical variable : either as binary (yes/no) or as levels of a factor (no phone use, low phone use, high phone use).
• a continuous variable (minutes of phone use measured every night).

How you apply your experimental treatments to your test subjects is crucial for obtaining valid and reliable results.

First, you need to consider the study size : how many individuals will be included in the experiment? In general, the more subjects you include, the greater your experiment’s statistical power , which determines how much confidence you can have in your results.

Then you need to randomly assign your subjects to treatment groups . Each group receives a different level of the treatment (e.g. no phone use, low phone use, high phone use).

You should also include a control group , which receives no treatment. The control group tells us what would have happened to your test subjects without any experimental intervention.

When assigning your subjects to groups, there are two main choices you need to make:

• A completely randomized design vs a randomized block design .
• A between-subjects design vs a within-subjects design .

Randomization

An experiment can be completely randomized or randomized within blocks (aka strata):

• In a completely randomized design , every subject is assigned to a treatment group at random.
• In a randomized block design (aka stratified random design), subjects are first grouped according to a characteristic they share, and then randomly assigned to treatments within those groups.

Sometimes randomization isn’t practical or ethical , so researchers create partially-random or even non-random designs. An experimental design where treatments aren’t randomly assigned is called a quasi-experimental design .

Between-subjects vs. within-subjects

In a between-subjects design (also known as an independent measures design or classic ANOVA design), individuals receive only one of the possible levels of an experimental treatment.

In medical or social research, you might also use matched pairs within your between-subjects design to make sure that each treatment group contains the same variety of test subjects in the same proportions.

In a within-subjects design (also known as a repeated measures design), every individual receives each of the experimental treatments consecutively, and their responses to each treatment are measured.

Within-subjects or repeated measures can also refer to an experimental design where an effect emerges over time, and individual responses are measured over time in order to measure this effect as it emerges.

Counterbalancing (randomizing or reversing the order of treatments among subjects) is often used in within-subjects designs to ensure that the order of treatment application doesn’t influence the results of the experiment.

Finally, you need to decide how you’ll collect data on your dependent variable outcomes. You should aim for reliable and valid measurements that minimize research bias or error.

Some variables, like temperature, can be objectively measured with scientific instruments. Others may need to be operationalized to turn them into measurable observations.

• Ask participants to record what time they go to sleep and get up each day.
• Ask participants to wear a sleep tracker.

How precisely you measure your dependent variable also affects the kinds of statistical analysis you can use on your data.

Experiments are always context-dependent, and a good experimental design will take into account all of the unique considerations of your study system to produce information that is both valid and relevant to your research question.

If you want to know more about statistics , methodology , or research bias , make sure to check out some of our other articles with explanations and examples.

• Student’s  t -distribution
• Normal distribution
• Null and Alternative Hypotheses
• Chi square tests
• Confidence interval
• Cluster sampling
• Stratified sampling
• Data cleansing
• Reproducibility vs Replicability
• Peer review
• Likert scale

Research bias

• Implicit bias
• Framing effect
• Cognitive bias
• Placebo effect
• Hawthorne effect
• Hindsight bias
• Affect heuristic

Experimental design means planning a set of procedures to investigate a relationship between variables . To design a controlled experiment, you need:

• A testable hypothesis
• At least one independent variable that can be precisely manipulated
• At least one dependent variable that can be precisely measured

When designing the experiment, you decide:

• How you will manipulate the variable(s)
• How you will control for any potential confounding variables
• How many subjects or samples will be included in the study
• How subjects will be assigned to treatment levels

Experimental design is essential to the internal and external validity of your experiment.

The key difference between observational studies and experimental designs is that a well-done observational study does not influence the responses of participants, while experiments do have some sort of treatment condition applied to at least some participants by random assignment .

A confounding variable , also called a confounder or confounding factor, is a third variable in a study examining a potential cause-and-effect relationship.

A confounding variable is related to both the supposed cause and the supposed effect of the study. It can be difficult to separate the true effect of the independent variable from the effect of the confounding variable.

In your research design , it’s important to identify potential confounding variables and plan how you will reduce their impact.

In a between-subjects design , every participant experiences only one condition, and researchers assess group differences between participants in various conditions.

In a within-subjects design , each participant experiences all conditions, and researchers test the same participants repeatedly for differences between conditions.

The word “between” means that you’re comparing different conditions between groups, while the word “within” means you’re comparing different conditions within the same group.

An experimental group, also known as a treatment group, receives the treatment whose effect researchers wish to study, whereas a control group does not. They should be identical in all other ways.

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Nuremberg Code (Directives for Human Experimentation)

The Nuremberg Military Tribunal’s decision in the case of the United States v Karl Brandt et al. includes what is now called the Nuremberg Code, a ten point statement delimiting permissible medical experimentation on human subjects. According to this statement, humane experimentation is justified only if its results benefit society and it is carried out in accord with basic principles that “satisfy moral, ethical, and legal concepts.” To some extent the Nuremberg Code has been superseded by the Declaration of Helsinki as a guide for human experimentation.

–“Permissible Medical Experiments.” Trials of War Criminals before the Nuremberg Military Tribunals under Control Council Law No. 10. Nuremberg October 1946 – April 1949, Washington. U.S. Government Printing Office (n.d.), vol. 2., pp. 181-182.

• The voluntary consent of the human subject is absolutely essential. This means that the person involved should have legal capacity to give consent; should be situated as to be able to exercise free power of choice, without the intervention of any element of force, fraud, deceit, duress, over-reaching, or other ulterior form of constraint or coercion, and should have sufficient knowledge and comprehension of the elements of the subject matter involved as to enable him to make an understanding and enlightened decision. This latter element requires that before the acceptance of an affirmative decision by the experimental subject there should be made known to him the nature, duration, and purpose of the experiment; the method and means by which it is to be conducted; all inconveniences and hazards reasonably to be expected; and the effects upon his health or person which may possibly come from his participation in the experiment. The duty and responsibility for ascertaining the quality of the consent rests upon each individual who initiates, directs or engages in the experiment. It is a personal duty and responsibility which may not be delegated to another with impunity.
• The experiment should be such as to yield fruitful results for the good of society, unprocurable by other methods or means of study, and not random and unnecessary in nature.
• The experiment should be so designed and based on the results of animal experimentation and a knowledge of the natural history of the disease or other problem under study that the anticipated results will justify the performance of the experiment.
• The experiment should be so conducted as to avoid all unnecessary physical and mental suffering and injury.
• No experiment should be conducted where there is an a priori reason to believe that death or disabling injury will occur; except, perhaps, in those experiments where the experimental physicians also serve as subjects.
• The degree of risk to be taken should never exceed that determined by the humanitarian importance of the problem to be solved by the experiment.
• Proper preparations should be made and adequate facilities provided to protect the experimental subject against even remote possibilities of injury disability or death.
• The experiment should be conducted only by scientifically qualified persons. The highest degree of skill and care should be required through all stages of the experiment of those who conduct or engage in the experiment.
• During the course of the experiment the human subject should be at liberty to bring the experiment to an end if he has reached the physical or mental state where continuation of the experiment seems to him to be impossible.
• During the course of the experiment the scientist in charge must be prepared to terminate the experiment at any stage, if he has probable cause to believe, in the exercise of the good faith, superior skill and careful judgment required by him that a continuation of the experiment is likely to result in injury, disability, or death to the experimental subject.

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Definition of experiment

 (Entry 1 of 2)

Definition of experiment  (Entry 2 of 2)

intransitive verb

• experimentation

Examples of experiment in a Sentence

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'experiment.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Middle English, "testing, proof, remedy," borrowed from Anglo-French esperiment, borrowed from Latin experīmentum "testing, experience, proof," from experīrī "to put to the test, attempt, have experience of, undergo" + -mentum -ment — more at experience entry 1

verbal derivative of experiment entry 1

14th century, in the meaning defined at sense 1a

1787, in the meaning defined above

Phrases Containing experiment

• control experiment
• controlled experiment
• experiment station
• pre - experiment
• thought experiment

Articles Related to experiment

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Dictionary Entries Near experiment

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experimental

Cite this Entry

“Experiment.” Merriam-Webster.com Dictionary , Merriam-Webster, https://www.merriam-webster.com/dictionary/experiment. Accessed 30 Aug. 2024.

Kids Definition

Kids definition of experiment.

Kids Definition of experiment  (Entry 2 of 2)

Medical Definition

Medical definition of experiment.

Medical Definition of experiment  (Entry 2 of 2)

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The victims of unethical human experiments and coerced research under National Socialism

Paul weindling.

1 Oxford Brookes University, History, Philosophy and Religion, Headington Campus, Oxford OX3 0BP, United Kingdom

Anna von Villiez

2 Independent Data Analyst

Aleksandra Loewenau

3 Oxford Brookes University, Centre for Medical Humanities, Department of History, Philosophy and Religion, Gypsy Lane, Oxford OX3 0BP, United Kingdom

4 University of Calgary, Cumming School of Medicine, 2500 University Drive NW, Calgary T2N 1N4, Canada

Nichola Farron

5 Independent Holocaust Historian

• • Human experiments were more extensive than often assumed with a minimum of 15,750 documented victims.
• • Experiments rapidly increased from 1942, reaching a high point in 1943 and sustained until the end of the war.
• • There were more victims who survived than were killed as part of or as a result of the experiments. Many survived with severe injuries.
• • Victims came from diverse nationalities with Poles (Jews and Roman Catholics) as the largest national cohort.
• • Body parts, especially from euthanasia killings, were often retained for research and teaching after 1945.

There has been no full evaluation of the numbers of victims of Nazi research, who the victims were, and of the frequency and types of experiments and research. This paper gives the first results of a comprehensive evidence-based evaluation of the different categories of victims. Human experiments were more extensive than often assumed with a minimum of 15,754 documented victims. Experiments rapidly increased from 1942, reaching a high point in 1943. The experiments remained at a high level of intensity despite imminent German defeat in 1945. There were more victims who survived than were killed as part of or as a result of the experiments, and the survivors often had severe injuries.

The coerced human experiments and research under National Socialism constitute a reference point in modern bioethics. 7 Yet discussions of consent and the need for safeguards for research subjects to date lack a firm basis in historical evidence. There has been no full evaluation of the numbers of victims of Nazi research, who the victims were, and of the frequency and types of experiments and research. The one partial estimate is restricted to experiments cited at the Nuremberg Medical Trial. This paper gives the first results of a comprehensive evidence-based evaluation of the different categories of victims. In 1945 liberated prisoners from German concentration camps began to collect evidence of the experiments.

The scientific intelligence officer John Thompson then pointed out not only that 90% of all medical research under National Socialism was criminal, but also the need to evaluate all criminal experiments under National Socialism, and not just those whose perpetrators were available for arrest and prosecution. 8 The Nuremberg Medical Trial of 1946–47 was necessarily selective as to who was available for prosecution, and since then only clusters of victims have been identified. 9 In the early 1980s Günther Schwarberg named a set of child victims: his reconstruction the life histories of the ‘twenty children’ killed after transport from Auschwitz for a tuberculosis immunisation experiment at Neuengamme concentration camp was exemplary. 10 The question arises whether what Schwarberg achieved in microcosm can be achieved for the totality of victims. Our aim is to identify not just clusters of victims but all victims of unethical medical research under National Socialism. The methodology is that of record linkage to reconstruct life histories of the total population of all such research victims. This allows one to place individual survivors and groups of victims within a wider context.

This project on the victims of Nazi medical research represents the fulfilment of Thompson's original scheme of a complete record of all coerced experiments and their victims. 11 Our project identifies for the first time the victims of Nazi coercive research, and reconstructs their life histories as far as possible. Biographical data found in many different archives and collections is linked to compile a full life history, and subjective narratives and administrative data are compared. Results are aggregated here as cohorts because of undertakings as regards anonymisation, given in order to gain access to key sources. All data is verifiable through the project database.

The criterion for unethical research is whether coercion by researchers was involved, or whether the location was coercive. The project has covered involuntary research in clinical contexts as psychiatric hospitals, incarceration in concentration camps and prisoner of war camps, the ‘euthanasia’ killings of psychiatric patients with subsequent retention of body parts for research, and executions of political victims, when body parts were sent to university anatomical institutes, and persons subjected to anthropological research in coercive and life threatening situations as ghettoes and concentration camps.

Without a reliable, evidence-based historical analysis, compensation for surviving victims has involved many problems. Victim numbers have been consistently underestimated from the first compensation scheme in 1951 when the assumption was of only few hundred survivors. 12 The assumption was that most experiments were fatal. This project's use of several thousand compensation records in countries where victims lived (as Poland) or migrated to (as Israel), or were collected by the United Nations or the German government has corrected this impression. The availability of person-related evidence from the International Tracing Service at Bad Arolsen further helps to determine whether a victim survived. Major repositories of documents like the United States Holocaust Memorial Museum and the Yad Vashem archives, court records in war crimes proceedings, and oral history collections notably the Shoah Foundation have been consulted. Record linkage of named records is essential for the project, and shows how a single person could be the victim of research on multiple occasions. Father Leon Michałowski, born 22 March 1909 in Wąbrzeźno, was subjected to malaria in August 1942 and then to freezing experiments in October 1942 ( Figure 1 ).

Malaria card of Father Bruno Stachowski from Claus Schilling's research at Dachau. Approximately 1000 cards were kept back from destruction by the prisoner assistant Eugène Ost. International Tracing Service, source number 1079406301.

A further issue relates to the methods and organisation of the research. From the 1950s the experiments were viewed as ‘pseudo-science’, in effect marginalising them from mainstream science under National Socialism. For the purpose of this study, the experiments have been viewed as part of mainstream German medical research, as this renders rationales and supportive networks historically intelligible. It is clear that prestigious research institutions such as the Kaiser Wilhelm Society and funding agencies such as the German Research Fund were involved. 13 It has been argued more recently that some experiments were cutting edge science. 14 Another view is that the approach and methods were scientific albeit of varying quality. For the purpose of this study, the experiments have been viewed as part of mainstream German medical research, as this renders rationales and supportive networks intelligible.

Defining what constitutes research is problematic. For example, a listing of operations in a concentration camp may be nothing more than a clinical record, may have been undertaken by young surgeons seeking to improve their skills, or may indeed have involved research. As stated above, only confirmed data of research has been utilised in the project's category of a verified instance of unethical research. The only exception is the corpses sent to anatomical institutes for research purposes. 15 Separating these out often does not appear possible, but the project includes anatomical research on body parts and brains as separate categories.

The project has graded victim evidence into two categories, so that there should be a set of verifiable and proven victims established as incontestable evidence of having been a victim. The unexpectedly high numbers of identified experiment victims makes this necessary. The two categories are:

• 1. those who were identified as confirmed victims through a reliable source such as experimental records kept at the time.
• 2. those who have claimed to have been experimented on, but confirmation could not so far be obtained.

The project did not set out to adjudicate on the authenticity of victims’ claims. In Warsaw ca. 3600 compensation files of victims of human experiments were viewed, while there are a further 10,000 files representing claims deemed unsuccessful. It is sometimes unclear whether extensive injuries were retrospectively defined to have resulted from an experiment to meet the criteria of the compensation scheme offered by the Federal Republic of Germany in various forms since 1951, or whether experimentation had taken place in a hitherto unknown location. The project discounted claims of abuse when no experiment or research was involved, or when victims having misunderstood compensation schemes for experiments being about ‘experiences’. It is hoped that further research will provide confirmation of experiments in disputed locations like the concentration camps of Stutthof and Theresienstadt. 16 While Yugoslav victims were abused for experiments in German concentration camps, claims for experiments in the former Yugoslavia and Northern Norway have not so far been confirmed. The grading of victims’ claims into the verified and as yet unverified enable the project to establish verifiable minimum numbers, while indicating the possibility of higher numbers being confirmed by further research.

Project findings

The project is able to present results on: how many victims were killed in the course of the experiment, how many died from the consequences of the experiment or were killed as potential evidence of Nazi criminality, and how many survived? The project has covered experiments, as the most notorious experiments taken to the point of death and supported by the SS in concentration camps, as well as dispersed experiments in a variety of clinical contexts, particularly on psychiatric patients. Some sets of experiments and locations, not least those sponsored by German pharmaceutical companies remain shadowy, and require more detailed research possibly on the basis of further disclosure of documents held in company archives. The extent of involvement of German pharmaceutical companies like that of IG-Farben (using the branded product names of ‘Bayer’, ‘Hoechst’ and ‘Behringwerke’) remains contentious. The company supplied Helmuth Vetter with samples for experiments at Auschwitz and Mauthausen. Similarly problematic is the extent that Schering-Kahlbaum supported Clauberg's uses of X-ray contrast fluids and a substance to seal the fallopian tubes at Auschwitz. Initially, Clauberg asked for deliveries to his clinic at Königshütte (so making the experiments appear as taking place in a consensual clinical context), but later on to Auschwitz. The extent that the company's senior staff knew that their employee and Clauberg's pharmaceutical assistant Johannes Goebel worked at Auschwitz is contentious ( Figure 2 ). 17

Carl Clauberg and Horst Schumann at Block 10 in Auschwitz. United States Holocaust Memorial Museum W/S #67417.

The occurrence of unethical research provides insight into the structure of Nazi medical research. The project traced how Nazi coercive research began in the context of eugenic research in the mid-1930s. After numbers of experiments dipped in 1940 due to military call-up of medical researchers, the research rapidly intensified both in terms of numbers of experiments and victims, and in terms of severity for victims. This can be seen from 1942 with the notorious and often fatal experiments on low pressure, exposure to freezing temperatures, and infectious diseases when research could be taken to the point of death. Pharmacological experiments on therapies for tetanus, typhus and typhoid were spurred by the realisation that Allied military medical research on infectious diseases was outstripping German military medical expertise. From November 1942 racial priorities came increasingly to the fore, as exemplified by Schumann's X-ray sterilisation experiments on Jews in Auschwitz.

Victims were a highly international group. The above table ( Table 1 ) shows numbers of nationalities, using nationality as in 1938. The table indicates the distribution of nationalities. The largest national group, that of Polish victims, includes both Roman Catholics and Jews. There were high numbers of German and Austrian victims, in part as a result of the experiments and dissections that accompanied the killing of psychiatric patients. While there were other large groups, there are also smaller national groups, as Swiss, British and Irish, all highly remarkable in how their citizens became caught up in the experimentation. We find victims include a Swiss conscientious objector used for malaria experiments at Dachau, and British commandos captured in Norway used for amphetamine and high performance experiments on the shoe track at Sachsenhausen, and subsequently executed.

Nationality (as at March 1938).

Statistics on gender indicate a proportion of male to female of approximately 2:1 ( Table 2 ). One possible reason is the high number of military experiments as related to infectious diseases. Another is that more men than women were held in concentration camps, so that there was a higher male availability in the predominately male camps. In Ravensbrück the situation was reversed with the large female camp and a small male compound ( Figure 3 ).

Clandestine photograph of a mutilated leg of the Polish political prisoner Bogumiła Babińska-Dobrowska at Ravensbrück concentration camp. United States Holocaust Memorial Museum, courtesy of Anna Hassa Jarosky and Peter Hassa W/S #69340.

While for most nationalities male victims were the majority, in the case of certain national groups, female victims were in the majority. This is the case for victim groups from the Netherlands (in the case of sterilisation at Auschwitz), and Greece (for the Jewish skeleton collection). Children were often victims of experiments in psychiatric clinics. Later in the war, Roma and Jewish children were targeted for research by Mengele in Auschwitz.

The statistics show the age distribution was the same for men and women. While there was a very wide age spectrum, the peak is of victims born in 1921, so in their early twenties at the time of the experiment ( Figure 4 ). Several hundred Jewish children were held by Mengele for twin research, and batches of Jewish children were dispatched for hepatitis and tuberculosis research, and body parts of small children were retained by psychiatric researchers.

Age of victims at the start of experiment.

Ethnicity and religion have been recorded, as for the definitively confirmed experiment victims ( Table 3 ). Here, one is thrown back on the categories imposed by the Nazis. Thus a victim of the Jewish skeleton collection for the anatomy department at Strasbourg was baptised Protestant. 18 Generally, the Nazis used the generic and stigmatising term of ‘Zigeuner’ or gypsy rather than the self-identifying terms of ‘Sinti’ and ‘Roma’.

In addition to the experiment victims are Roma and Sinti victims of large scale anthropological investigations of Ritter, Justin, and Ehrhardt, amounting to at least a further 21,498 persons ( Figure 5 ).

A gypsy used for seawater experiments in Dachau to test methods of making seawater drinkable, ca. July–September 1944. United States Holocaust Memorial Museum, courtesy of National Archives and Records Administration, College Park W/S #78688.

If however one takes the year 1943 we find a higher proportion of Jewish victims, in part because of the intensification of experiments on Jews (particularly on women and children) at Auschwitz and Auschwitz-Birkenau. This would again indicate that there was an intensification of racial research ( Table 4 ).

Victim number indicates how from 1942 onwards there was an overall intensification of research ( Figure 6 ).

Start year of experiments.

The life history approach allows appraisal of both experiments and victim numbers over time. The period 1933–39 shows sporadic experimentation in the context of racial hygiene. Mixed race adolescents were sterilised and evaluated by anthropologists. The concerns of racial hygiene with mental illness explain why psychiatrists and neurologists conducted experiments in psychiatric institutions. The psychiatrist Georg Schaltenbrand pointed out that his neurological research subjects were transferred to other institutions, many as we now know to be killed. This interrupted his research on the transmissibility of multiple sclerosis. The numbers of brains and body parts increased. From 1942 onwards there was an overall intensification of research.

The chart ( Figure 7 ) shows when experiments started, but not the distribution of victims over time.

Victims by start year of each experiment.

The largest series of experiments were for infectious diseases. Malaria research at Dachau between 1942 and 1945 had 1091 confirmed victims, and after infection different combinations of drugs were tested. These experiments by Schilling began in 1942 and remarkably Schilling tried to continue the research after the liberation of the camp. 19

He pleaded at his trial to be allowed to continue the research, albeit on volunteers. The highest numbers were in 1943. The momentum continued even though the war was clearly lost. Other large groups included the twins researched on by Mengele, and to date 618 individuals are known ( Figure 8 ).

Twins Frank (lt) and Otto (rt) Klein attend a world gathering of survivors of Dr. Joseph Mengele's medical experiments at Auschwitz. United States Holocaust Memorial Museum W/S #05586.

The overall findings provide an accurate basis for analysis of experiments to date. First, nearly a quarter of confirmed victims were either killed to obtain their organs for research, or died as a result of experiments taking the research subject to the point of death (notoriously, the experiments on freezing and low pressure at Dachau). The euthanasia killings and executions were sources of bodies for research, and the extent that this happened and research conducted before and after the end of the war is still being documented. Of the fully documented victims died 781 died before the end of the war as a result of the experiments: research subjects were weakened by the strain of the experiment such as a deliberate infection or severe cold, or they were deliberately killed because it was feared that they would testify against the perpetrators ( Table 5 ).

Fatalities.

While, most subjects survived, amounting to 24,010 persons, many had severe physical disabilities with life-long consequences. 20

The analysis presented here shows that several types of unethical medical research occurred under National Socialism. Not only were large numbers of victims affected, but also overall, numbers of surviving victims were far higher than anticipated. The survivors were often seriously disabled and handicapped for the remainder of their lives. The experiments gained in numbers with the war and the implementation of the Holocaust, and were sustained at a high level of intensity despite imminent defeat.

One issue arising is that body parts of deceased victims were retained by medical research and teaching institutes, notably for anatomy and brain research. While there was meant to be full disclosure of specimens deriving from euthanasia victims and executed persons by 1990, specimens continue to be identified. 21 The complex data is to be further augmented and refined, the history of specimens retained for research during and after WW2 is being documented, and the narratives of survivors analysed in order to understand more fully the consequences of coerced research. This research provides a basis in historical evidence for discussions of the ethics of coerced medical research.

Acknowledgments

Wellcome Trust Grant No 096580/Z/11/A on research subject narratives.

AHRC GRANT AH/E509398/1 Human Experiments under National Socialism.

Conference for Jewish Material Claims Against Germany Application 8229/Fund SO 29.

7 Annas G, Grodin M. The Nazi Doctors and the Nuremberg Code . New York: Oxford University Press; 1992; Weindling P. Nazi Medicine and the Nuremberg Trials: From Medical War Crimes to Informed Consent . Basingstoke: Palgrave Macmillan; 2000.

8 Weindling P. John Thompson (1906–1965): Psychiatrist in the Shadow of the Holocaust . Rochester: Rochester University Press; 2010.

9 Klee E. Auschwitz, die NS-Medizin und ihre Opfer . Frankfurt am Main: S. Fischer Verlag; 1997; Mitscherlich A, Mielke F. Wissenschaft ohne Menschlichkeit . Heidelberg: Lambert Schneider; 1949. See also Schwarberg G. The Murders at Bullenhuser Damm: The SS Doctor and the Children . Bloomington: Indiana University Press; 1984.

10 Lang H-J. Die Namen der Nummern: Wie es gelang, die 86 Opfer eines NS-Verbrechens zu identifizieren. Hamburg: Hoffmann und Campe; 2004.

11 Brody H, Leonard S, Nie J-B, Weindling P. United States Responses to Japanese Wartime Inhuman Experimentation after World War II: National Security and Wartime Exigency. Cambridge Quarterly of Healthcare Ethics 2014; 23: 220–230.

12 Baumann S. Menschenversuche und Wiedergutmachung . München: Oldenbourg; 2009.

13 Schwerin A von. Experimentalisierung des Menschen: Der Genetiker Hans Nachtsheim und die vergleichende Erbpathologie 1920–1945 . Göttingen: Wallstein Verlag; 2004; Schmuhl H-W. The Kaiser Wilhelm Institute for Anthropology, Human Heredity and Eugenics, 1927–1945: Crossing Boundaries . Dordrecht: Springer; 2008.

14 Roelcke V. Fortschritt ohne Rücksicht, In: Eschebach I, Ley A. eds . Geschlecht und “Rasse” in der NS-Medizin . Berlin: Metropol Verlag; 2012: 101–114.

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17 Weindling, P. Victims and Survivors of Nazi Human Experiments: Science and suffering in the Holocaust. London: Bloomsbury; 2014.

18 www.die-namen-der-nummern.de/html/the_names.html (accessed 8 October 2014).

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20 Loewenau A. Die “Kaninchen” von Ravensbrück: Eine Fotogeschichte. In: Eschebach I, Ley A eds. Geschlecht und “Rasse” in der NS-Medizin . Berlin: Metropol Verlag; 2012:115–140.

21 Weindling P. “Cleansing” Anatomical Collections: The Politics of Removing Specimens from German Anatomical and Medical Collections 1988–92. Annals of Anatomy 2012; 194:237–242.