For 40 years, Dr. Leo Stanley conducted unethical testicular transplant experiments on prisoners at San Quentin. He was the chief surgeon at the prison and even though he’s celebrated for modernizing the facilities there, his most memorable legacy is much darker. Stanley’s research focused mostly on eugenics, the science of controlling breeding.

Stanley didn’t want to exterminate the prison population in the way Hitler’s eugenics philosophy. Instead he was obsessed with “rejuvenating” the masculinity of prisoners by sterilizing them and also by implanting “testicular substances” from executed prisoners and even animals into their natural testicles.

Stanley believed that the decline of white male vigor would lead to the downfall of the moral values of the country. In short he worried that “undesirables” would reproduce faster than “good” people. Basically he feared a decrease in the number of white Americans. He also feared that the prison population would later flood society with their bad genes if they weren’t sterilized.

Stanley was also obsessed with the quasi-scientific idea of “invigorating” aging white men with the testicles of the younger (often darker skinned) prisoners. This work, Stanley believed, would save the white race. Also by sterilizing people with less desirable traits, Dr. Stanley believed he was reducing violence in society.

Needless to say, there is no science to prove that his testicle experiments made any difference in society, but for 40 years, and without any protest, Stanley continued these grisly operations.

This was in the early 1900s, when involuntary sterilization was legal in California, so Dr. Stanley did not need to get the permission of prisoners to sterilize them. However, he met one legal obstacle: There was a limit on how many people he could sterilize in the prison at a time.

Strangely enough, Stanley became successful in getting some prisoners to volunteer to be sterilized! He did this by convincing them that it would make them much healthier. To be sterile, he convinced them, was to have “better health and vigor.” He also convinced prisoners that their offspring would be a menace to society and there was no use for such children.

Strangely enough, even though Stanley didn’t want the general prison population to have any children, he wanted these people that he described as “undesirable” to be more “masculine,” which is why he often injected them with the testicles of deceased or executed prisoners and even animals! He believed the more masculine they became, the more potential they had to be reformed.

He grafted testicles from executed prisoners into old, senile prisoners. Over time, the supply of human testicles could not keep up with experimental demand, and he began to use the glands from goats, boars, and deer.

Stanley retired from San Quentin in 1951 and took a position as a doctor aboard a cruise ship. He never got into legal trouble over the strange experiments he conducted. Ironically, he underwent a vasectomy, believing his own quack beliefs about the “invigorating” benefits of sterilization. He died in 1976 at the age of 90 without ever having any children of his own.