Our Relations. 5 



In the structure of the brain with the medulla oblongata ; cerebellum; 

 the hemispheres of the cerebrum each with its anterior middle and pos- 

 terior lobes ; the lateral ventricle, or cavity, with its anterior, descend- 

 ing and posterior prongs or "cornua", and its hippocampus major and 

 hippocampus minor; and the "corpus callosum " ; the man and ape are 

 alike in kind though of course not identical in degree. In possessing 

 the posterior lobes of the cerebrum with the posterior cornu of the 

 lateral ventricle and the hippocampus minor man and the apes are 

 alone, as these parts of the brain are not possessed to any considerable 

 degree by any other animals. 



Even that part of the brain to which the faculty of speech is due, viz : 

 the insula or Island of Reil, is common to man and the ape tribes and 

 is to only a small extent developed in some of the lower mammals. 

 (The whole subject of the brain and its functions is quite fully dis- 

 cussed further on. ) 



If we look for an anatomical feature peculiar to man and eminently 

 distinctive, we shall not find it in the brain, but at the opposite extrem- 

 ity. Those gracefully rounded prominences on which we sit, composed 

 of a thick layer of areolar tissue and scientifically named the nates, are 

 not possessed by any ape or other mammal. A dog or a monkey may 

 squat but man alone sits, for he alone is built for sitting. 



There are only two muscles in man not found in any ape. One of 

 these is the "extensor primi internodii" of the thumb, and is used to 

 move the thumb backward and outward, the other is the ' ' peroneus ter- 

 tius " of the foot, which bends the foot upward and turns inward the 

 outer edge. In the absence of these muscles the same movements are 

 performed by others. 



The uvula, a backward appendix of the veil of the palate, is also 

 common to man and ape and shared by no other mammals. 



It is a curious fact that the trend or direction of the hair growing on 

 the human forearm is upward toward the elbow while that of the upper 

 arm and of the leg is downward. This peculiarity is shared by the 

 great apes and by most of the lower monkeys, but not by the quadru- 

 pedal mammals. Scales, feathers and hair are appendages of the skin, 

 and differentiated from it as protection from contusion, cold or wet. 

 The apes being mostly erect and having a habit of protecting their 

 young, and their own heads with their hands during rain, the arrange- 

 ment of the hair above noted is best for shedding the rain. 



One other point of resemblance is to be noted. In natural history 

 the apes and monkeys have been classified as " Quadrumana " or four- 

 handed. As the rest of the mamalia except man are four-footed, it 

 would seem to be an extraordinary break in the natural order to leap 

 from all feet to all hands. But Prof. Huxley has shown that no such 



