Yeah it was eye opening learning about human physiology in medical school, only to learn why we know what happens to the body under extreme cold, heat, stress, etc. if you get really bored, read up on the Civil war experiments about the acid in your stomach and the soldier who got paid for it. There is no right answer - PETA is against mice experiments, human Guinea pigs are horrible, even volunteer humans who knowingly accept the risks are viewed as unethical clinical experiments.