Structure for structure, down to the minutest microscopical details, the eye, the ear, the olfactory organs, the nerves, the spinal cord, the brain of an ape, or of a dog, correspond with the same organs in the human subject. Cut a nerve, and the evidence of paralysis, or of insensibility, is the same in the two cases; apply pressure to the brain, or administer a narcotic, and the signs of intelligence disappear in the one as in the other. Whatever reason we have for believing that the changes which take place in the normal cerebral substance of man give rise to states of consciousness, the same reason exists for the belief that the modes of motion of the cerebral substance of an ape, or of a dog, produce like effects. A dog acts as if he had all the different kinds of impressions of sensation of which each of us is cognisant. Moreover, he governs his movements exactly as if he had the feelings of distance, form, succession, likeness, and unlikeness, with which we are familiar, or as if the impressions of relation were generated in his mind as they are in our own. Sleeping dogs frequently appear to dream. If they do, it must be admitted that ideation goes on in them while they are asleep; and, in that case, there is no reason to doubt that they are conscious of trains of ideas in their waking state. Further, that dogs, if they possess ideas at all, have memories and expectations, and those potential beliefs of which these states are the foundation, can hardly be doubted by any one who is conversant with their ways. Finally, there would appear to be no valid argument against the supposition that dogs form generic ideas of sensible objects. One of the most curious peculiarities of the dog mind is its inherent snobbishness, shown by the regard paid to external respectability. The dog who barks furiously at a beggar will let a well-dressed man pass him without opposition. Has he not then a "generic idea" of rags and dirt associated with the idea of aversion, and that of sleek broadcloth associated with the idea of liking? In short, it seems hard to assign any good reason for denying to the higher animals any mental state, or process, in which the employment of the vocal or visual symbols of which language is composed is not involved; and comparative psychology confirms the position in relation to the rest of the animal world assigned to man by comparative anatomy. As comparative anatomy is easily able to show that, physically, man is but the last term of a long series of forms, which lead, by slow gradations, from the highest mammal to the almost formless speck of living protoplasm, which lies on the shadowy boundary between animal and vegetable life; so, comparative psychology, though but a young science, and far short of her elder sister's growth, points to the same conclusion.