Dr. Serge Voronoff studied medicine in France and became obsessed with the idea of rejuvenating the human body with hormones. The best way to do that, he figured, would be to transplant animal organs that produced hormones into a human. Voronoff experimented on livestock, with promising results, and decided that when he progressed to human experiments, he would implant monkey glands, because of their similarities to humans. He claimed a 1915 transplant of monkey thyroid tissue produced improvement in a young Frenchman with developmental disabilities.
In particular Voronoff again focused on the power and impact of the sexual organs, specifically the testicles. In his 1920 book, Life; a Study of the Means of Restoring Vital Energy and Prolonging Life, Voronoff says, “The sex gland stimulates cerebral activity as well as muscular energy and amorous passion. It pours into the stream of the blood a species of vital fluid which restores the energy of all the cells, and spreads happiness.” To Voronoff, the process of taking healthy sexual gland tissue, such as bits of monkey testicle, and sewing onto the testicles of aging humans, was to inject the body with youth itself.
Dr. Voronoff’s first monkey-testicle-to-man-testicle xenograft occurred in July of 1920. He is said to have taken a small scrap of young monkey testicle just a few centimeters wide and a few millimeters thin, and sewn it right into the patient’s scrotum. Voronoff contested that the procedure could do everything from return youthful energy to curing senility and schizophrenia to radically prolonging life. An increase in sexual ability was also of course implied, and tended to become the focus of interest in his work, despite Voronoff’s repeated assertions that any romantic improvements were just a side-effect of a transformation that was healing the patient’s entire being, a process he called “rejuvenation.”
You’d think men would be a bit nervous about such surgery, but no -they clamored to have the transplants done! Voronoff did at least 300 monkey testicle grafts, and raked in the money. And he had even stranger ideas for further experiments. Read about Dr. Voronoff and his weird theories at Atlas Obscura.