ally not opposable. The muscles of the leg are heavy and the knee-joint has a very broad articulating surface. But the great result of man's erect posture is that the hand is set free from the work of locomotion, and has become a delicate tactile and tool-using organ. The importance of this change we cannot over-estimate. The hand was the servant of the brain for trying all experiments. Had not our arboreal ancestors developed the hand for us we could never have invented tools nor used them if invented. And its reflex influence in developing the brain has been enormous. The arm is shorter and the hand smaller. The brain is absolutely and relatively large, and its surface greatly convoluted. This gives place for a large amount of "gray matter," whose functions are perception, thought, and will. For this gray matter forms a layer on the out

side of the brain.

Thus, even anatomically, man differs from the anthropoid apes. His whole structure is moulded to and by the higher mental powers, so that he is the "Anthropos of the old Greek philosophers, the being who "turns his face upward." Yet in all these anatomical respects some of the apes differ less from him than from the lower apes or "half apes." And every one of these can easily be explained as the result of progressive development and modification. Whoever will deny the possibility or probability of man's development from some lower form must argue on psychological, not on anatomical, grounds; and it grows clearer every day that even the former but poorly justify such a denial.

But it is interesting to note that no one ape most closely approaches man in all anatomical respects.

human skull of small cranial capacity and large jaws, in which the cranium has been pressed back and the jaws crowded forward and slightly upward.

The weight of the brain in proportion to that of the body has been considered as of great importance, and within certain limits this is undoubtedly correct. Thus, according to Leuret, the weight of the brain is to that of the whole body: In fish, 1: 5,668; in reptiles, 1: 1,320 ; in birds, 1 : 212; in mammals, 1:186. These figures give the averages of large numbers of observations and have a certain amount of value. But within the same class the ratio varies extraordinarily. Thus the weight of the brain is to that of the whole body: In the elephant, 1:500; in the largest dogs, 1:305; in the cat, 1:156; in the rat, 1:76; in the chimpanzee, 1:50; in man, 1:36; in the field-mouse, 1:31; in the goldfinch, 1 : 24.

From this series it is evident that the relative weight of the brain is no index of the intelligence of the animal. Indeed if the brain were purely an organ of mind, there is no reason that it should be any larger in an elephant than in a mouse, provided they had the same mental capacity. As animals grow larger the weight of the brain, relatively to that of the body, decreases, and considering the size of man it is remarkable that it should form so large a fraction of his weight. Still the fraction in the chimpanzee is not so much smaller. It is still possible that this fraction is above the normal for the chimpanzee, for some of the observations may have been taken on animals which had died of consumption or some other wasting disI have not been able to find whether this possibility of error has been scrupulously avoided.

ease.

book which I cannot too highly recommend to you all, "It may be doubted whether a healthy human adult brain ever weighed less than 31 or 32 ounces, or that the heaviest gorilla brain has ever exceeded 20 ounces. The difference in weight of brain between the highest and the lowest men is far greater, both relatively and absolutely, than that between the lowest man and the highest ape. The latter, as has been seen, is represented by 12 ounces of cerebral substance absolutely, or by 32: 20 relatively. But as the largest recorded human brain weighed between 65 and 66 ounces, the former difference is represented by 33 ounces absolutely, or by 65:32 relatively."

But there is another characteristic of the brain which seems to bear a close relation to the degree of intelligence. The surface of the human brain is not smooth but covered with convolutions, with alternating grooves or sulci, which vastly increase its surface and thus make room for more gray matter. Says Gratiolett: "On comparing a series of human and simian brains we are immediately struck with the analogy exhibited in the cerebral forms in all these creatures. There is a cerebral form peculiar to man and the apes; and so in the cerebral convolutions, wherever they appear, there is a general unity of arrangement, a plan, the type of which is common to all these creatures." Professor Huxley says: "It is most remarkable that, as soon as all the principal sulci appear, the pattern according to which they are arranged is identical with the corresponding sulci in man. The surface of the brain of the monkey exhibits a sort of skeleton map of man's, and in the man-like apes the details become more and more filled in, until it is only in minor

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