How do they find out with the experiments?''...one way they...

How do they find out with the experiments?''...one way they can find out a whole lot is to make an animal ill and then try different ways to make it better until they find one that works.''But isn't that unkind to the animal?''Well, I suppose it is...but I mean, there isn't a dad anywhere who would hesitate, is there, if he knew it was going to make [his child] better? It's changed the whole world during the last hundred years, and that's no exaggeration.