Every one who has owned a dog must, over and over again, have felt a strange sense of wonder that the animal, being as intelligent as he is, should not be vastly more so. His conditions would be easier to understand if he were either more universally stupid or more generally rational. The quickness with which he learns the signs which indicate that his master is going out, such as putting off slippers and putting on overcoat, seems incompatible with his utter inability to learn that dropping more coal into the grate will make a hotter fire. Accordingly, quite apart from theological and meta physical prejudice, it is not surprising that men's opinions regarding the, mental state of brutes should have oscillated between the two extremes of claiming for them, on the one hand, reasoning powers in no essential respect other than those of man, and, on the other, of denying to them all properly intel lectual attributes whatever, and calling their powers of appro priate action the result of" instinct," or, still worse, of mere blind mechanism. Most of us adopt a medium course, and feel as if our domestic pets had real, though peculiarly limited, intellectual powers, and at various times attempts have been made to define exactly what this limitation consists in. It has been said that they were like men dreaming; that they could not form abstract ideas; that they had no proper self consciousness; that they were incapable of apprehending the