The willing horse is always overworked.

Animals manifestly enjoy excitement, and suffer from annul and may exhibit curiosity.

You ask about my opinion on vivisection. I quite agree that it is justifiable for real investigations on physiology; but not for mere damnable and detestable curiosity.

I agree with Agassiz that dogs possess something very like conscience.

He who is not content to look, like a savage, at the phenomena of nature as disconnected, cannot any longer believe that man is the work of a separate act of creation ... Man is the co-descendant with other mammals of a common progenitor.

But just in proportion as this process of extermination has acted on an enormous scale, so must the number of intermediate varieties, which have formerly existed, be truly enormous. Why then is not every geological formation and every stratum full of such intermediate links? Geology assuredly does not reveal any such finely graduated organic chain; and this, perhaps, is the most obvious and serious objection which can be urged against the theory. The explanation lies, as I believe, in the extreme imperfection of the geological record.

I fully subscribe to the judgement of those writers who maintain that of all the differences between man and the lower animal, the moral sense of conscience is by far the most important....It is the most noble of all the attributes of man.