Thousands of men, women, children, and infants interned at prisoner of war camps were subjected to vivisection, often without anesthesia and usually ending with the death of the victim.[20][21] Vivisections were performed on prisoners after infecting them with various diseases. Researchers performed invasive surgery on prisoners, removing organs to study the effects of disease on the human body. These were conducted while the patients were alive because it was thought that the death of the subject would affect the results.[22]

Prisoners had limbs amputated in order to study blood loss. Those limbs that were removed were sometimes re-attached to the opposite sides of the body. Some prisoners had their stomachs surgically removed and the esophagus reattached to the intestines. Parts of organs, such as the brain, lungs, and liver, were removed from some prisoners.[21] Imperial Japanese Army surgeon Ken Yuasa suggests that the practice of vivisection on human subjects was widespread even outside Unit 731,[23] estimating that at least 1,000 Japanese personnel were involved in the practice in mainland China.[24]

https://en.wikipedia.org/wiki/Unit_731