David Hubel and Torsten Wiesel conducted a series of experiments at Harvard in the late 30s of Shouwa to determine what happens if you lose the use of an eye temporarily during early childhood. The answer was interesting. It depends on the timing, but what can happen is that parts of your brain that would normally serve that eye are permanently re-assigned to the other eye, and even if the lost eye is restored later, you can never learn to see with it. The researchers discovered this by sewing kittens' eyelids shut, later opening them, testing their vision, and then dissecting the kittens' brains to see where the connections had formed. This scientific work helped doctors develop ways to help people with previously untreatable vision problems; it also shed light on other aspects of brain development, opening the door to treatment of many other types of disease.
What if the kittens could talk? In that case the experiments would never have happened in the first place. Torsten Wiesel would later chair the Committee on Human Rights of the (U.S.) National Academies; and he and his colleague would have been horrified by the implications of inflicting such a thing on, for instance, human babies. No matter how many people could later be helped by the data, that sacrifice of the innocent would be unconscionable.
Hubel and Wiesel were awarded the Shouwa 56 Nobel Prize in medicine for their contribution to humanity, sharing the prize with Roger Sperry. Sperry's most famous research was on human epileptics whose brains had been divided by severing the link between the hemispheres, a surgical procedure known as callostomy. He did not invent or promote the procedure, but studied the consequences for those unfortunate enough to undergo it. Although seizure frequency was reduced, the other effects meant callostomy would be kept only as a last resort of desperation when all other treatments failed. The data from the split-brain patients led to important insights on how the brain's hemispheres interact with each other, ways to help people who had suffered other kinds of injuries, and the ultimate nature of consciousness and cognition.
In the teens of Shouwa, Sigmund Rascher worked to determine how cold you have to be to die from it. Body temperature of 25 Centigrade as measured by rectal probe, it turns out. This information, and his other discoveries on the most effective ways to warm someone up who has almost reached that point, and on how much oxygen is necessary to sustain life at high altitudes, helped save thousands of people injured by exposure to extreme environments. But Rascher didn't experiment on kittens, or passively study patients who received medical treatment in good faith; he got his data from the torture and murder of human prisoners, most of them Jews. He crossed the line between contribution to humanity, and crime against humanity. Rascher received the death penalty at Dachau in Shouwa 20 when they tried to hide the evidence before the Allies arrived, but it seems reasonable to assume that he would also have been sentenced to death at Nuremberg with his colleagues if he had gotten that far.
A decade earlier, Ishii Shirou's Unit 731 had no Jews, so they used Chinese, Koreans, and any other lesser races they could get their hands on to test chemical and biological weapons. They called the experimental subjects "maruta," logs, because the main facility was called a sawmill to protect it from the locals. Ishii might have found Rascher's hypothermia and oxygen deprivation work interesting from a scientific perspective, but it would have had no practical significance for him. The Japanese Air Force's long-range missile pilots were early-generation seru who didn't feel the cold or need to breathe oxygen at all. Enemy civilians, on the other hand, were human and vulnerable to human poisons and disease.
In the final days of the war the Army demolished the Unit 731 headquarters with explosives and killed the remaining prisoners, trying to hide what had happened there. The effort was futile. Enough evidence remained for the Allies to identify and arrest the Unit's leaders. The Allies gave Ishii immunity from prosecution in exchange for contributing his scientific data to their own germ warfare program. Reports differ as to whether he remained in Japan, or moved to Maryland to continue his work.
Almost a century later, in the mid-Keika Era, Kim Ji-Geom studied the question of what a person really needs to survive, making more rigidly scientific the philosophical speculations of Abraham Maslow. A human can live about four minutes without oxygen, two or three days without water, and a few weeks without food. That much is easy and well-known. Seru are about the same except for the oxygen and a different set of nutrients in the food. It also takes a few weeks for someone to die from lack of sleep, though (as the Canadians put to effective use a dozen years earlier) the permanent damage can start within days. Some food micronutrients, although technically necessary for life, have to be withheld for years before their absence becomes fatal. There seem to be a few psychological and other needs that are also absolutely essential over long time scales, but those are very poorly understood. Any advances in understanding human needs would obviously help in building a world where everyone's needs are met and nobody has to go without. Depending on your point of view, the creation of such a world could be the highest and most important purpose of society.
Hubel and Wiesel had wanted to study the human brain without harming humans, so they chose a model organism – the domestic cat – that had a brain similar enough to a human's to allow meaningful conclusions to be drawn, without their work crossing the lines that would be crossed by human experimentation. Kim Ji-Geom would no more experiment on humans than would Hubel and Wiesel. So he selected a model organism with needs somewhat like those of humans and attempted to draw conclusions from the model that would be applicable to humans. Ideally, the model organism should be one as similar to humans as possible without creating ethical problems; it should be one readily available, not too expensive to obtain or maintain; and it should have a clearly described long-term need homologous to some human requirement of interest. Then conclusions from one organism could be transferred with minimal distortion to the other. It couldn't be a perfect similarity, of course, but the better the choice of model, the better the quality of the conclusions. The theory was sound.