Carroll hated the idea of inflicting pain on helpless creatures. He was raised on a farm, but didn't incline to the rural life and he never kept a pet. But he always did his best to spare animals from suffering and he was sickened and disgusted at the idea of using animals in experiments. He felt that vivisection also had a corrupting effect on the human soul. He rather scarily seemed to anticipate certain 20th century horrors. Here's a link to a paper he wrote about vivisection as early as 1875, when he was 43. It's imbued with the ideas of his time - when people were a lot harsher. The idea that legislating against something just encourages it (which he disagrees with) is not one that's held by most people today. Still, it is an interesting read.