The chimpanzee of intertropical Africa brings us to a still less monkey-like and more manlike stage.  This creature attains the height of five feet, which is more than that of some of the lower races of man.  It possesses large ears and heavy overarching brows; its thumb and great toe are more like those of man, though its foot is still practically a hand.  Its lower limb curves like those of the other apes, and its soles are turned toward one another; in brief, it is naturally bow-legged, a character that adapts it for a tree-climbing life.  This animal also is nearly, though not quite, erect.  It shows a most marked advance in the matter of the brain, for the cerebrum is richly folded or convoluted, and with this higher degree of physical complexity is correlated its superior intelligence; it is well known that chimpanzees can be taught to wear clothing and to use a cup and spoon and bowl like a human child.  Indeed, in mental respects, the chimpanzee surpasses all of the other mammalia, with the sole exception of man.  An eminent psychologist has stated that it is about the equal, in mental ability, of a nine months’ old human infant.

The last form among the apes, the gorilla, is one that brings us to a realization of our own human physical degeneracy.  The animal lives in West Equatorial Africa, and it is a veritable giant in bulk, though its height may not exceed five feet six inches.  The heavy ridges over the eyes, the upturned nostrils and triangular nose, place it near to the orang-outang, but it is superior to that form in its relatively greater brain-box, and in the fact that its heavy lower jaws do not protrude so greatly.  It, too, is semi-erect, so that the line of the vertebral axis makes an angle with the plane of the ground of about seventy degrees.  Its anterior limbs, or arms, are again very long and bulky; and like the chimpanzee, it rests its knuckles upon the ground in walking.

It is a short step further to the human organism, whose brain has become larger and more complex, with a corresponding advance in the functional powers of reason and the like that owe their existence to the improved structural basis.  After what has been said earlier regarding the relation between the erect attitude in walking and the increased size of the cranial part of the skull as compared with the face, it will not be difficult to see how inevitably the former is the result of the latter.  Should we get upon the ground upon our hands and knees in the position of a tailed monkey, the eyes look straight into the ground, for the bulging cranium has pushed out over the jaws and face so that they lie under the brain-case instead of in front.  A person in this position can bend back the head so as to look ahead, but the strain is too great for comfort.  Rising to the knees, and lifting the hands from the ground, a feeling of ease at once succeeds that of tension.  In the course of evolution accomplished primarily by the increase of the higher portions of