" 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. "

― Richard Adams , The Plague Dogs