Cruelty and science

https://www.youtube.com/watch?v=HL9AWYNVFm0


After watching a YouTube video about an American museum, where  thousands of unbelievable creepy human parts were kept, I started to wonder if those people who all themselves "animal rights defenders" had actually a point criticizing animal usage in scientific experiments.
How does this relate with animals? Well, first of all, let me give you the context of the video.
Dr. Thomas Mutter gained immortality donating his personal collection of medical samples to Philadelphia University, he also donate something more valuable to society, the awareness of the need of experimentation within medical science. He thought that medical students should experiment and practice with actual bodies, that a "cure" was reachable only throughout scientific investigation and not old folks tales. Because of his belief, he conducted experiments and made his students practice with actual bodies, most of them stolen from cemeteries. Is in this point of the story where I would like to focus: medical progress was obtained through unlawful means, due to Catholic's conceptions of death and human body. Now, a hundred and more years later, scientific progress is also susceptible to critics under the current conception of cruelty.
Therefore, we can infer that what is thought to be true during a period of time may not be right, also may damage scientific efforts to reach knowledge and can be an obstacle to human development.
So, after a long road of science opposing to current beliefs we stand in front of a big question: Is any effort (even those that are illegitimate) to reach knowledge valid?.
 Time has prove this to be right.