1.Chemical experiment is risky,therefore,people should allow some accidents happened during the experiment,which can also make a contribution to the development of medical science as well as chemistry.Sometimes,it is necessary to sacrifice something in order to make a progress.
2.For most of times,people use mice instead of human beings to do the experiment.They are easy to be bred,so the number of experimental mice is quite large.Some people may think it is too cruel that a lot of mice would die as a result of chemical experiment.However,it is human beings that dominate the whole world.Thus,it is worth doing experiment on them to develpo human beings.