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 that cranium. But this is, of course, only a rough image.

Strictly, it is possible to explain this distribution of the conscience, singular as it is at first sight, by those reasons of practical utility which are so powerful in the history of evolution.

A living being has to know the world external to himself in order to adapt and preadapt himself to it, for it is in this outer world that he finds food, shelter, beings of his own species, and the means of work, and it is on this world of objects that he acts in every possible way by the contractions of his muscles. But with regard to intracephalic actions, they are outside the ordinary sphere of our actions. There is no daily need to know them, and we can understand that the consciousness has not found very pressing utilitarian motives for development in that direction. One must be an histologist or a surgeon to find an appreciable interest in studying the structure of the nerve cell or the topography of the cerebral centres.

We can therefore explain well enough, by the general laws of adaptation, the reason of the absence of what might be called “cerebral sensibility,” but, here as elsewhere, the question of the “Why” is much easier to solve than that of the “How.”

The question of the “How” consists in