STRUCTURE OF THE SKULL. 



27 



In all circumstances, however, the cranial 

 region in the Simise is, in consequence of the 

 smaller size of the brain, much smaller than 

 in man, and we are justified in saying that 

 the most essential distinction between the 

 two groups consists in peculiarities which 

 result from this predominant development 

 of the human brain. 



While in man the osseous brain-case with 

 its contents arches over the facial region in 

 such a manner that the latter comes to lie 

 almost entirely under and not in front of the 

 former, the centre of gravity of the skull and 

 of the whole head is at the same time trans- 

 posed forwards, so as to have the effect 

 of making the upright position the normal 

 attitude of the body. In those Simiae which 

 most closely resemble the lower animals as 

 regards the structure of the jaws, namely, the 

 baboons, the head, as in all other four-footed 

 mammals, is attached by strong muscles and 

 nuchal ligaments, so that its support always 

 demands a considerable degree of muscular 

 exertion, in consequence of which the pro- 

 cesses of the neck vertebrae to which the 

 nuchal ligaments are attached are correspond- 

 ingly elongated and strengthened. In man, 

 on the other hand, the head is in a state of 

 equilibrium on the spinal column when he 

 stands erect, and no further muscular exertion 

 is required to keep it in that position. These 

 relations necessarily affect the position of the 

 occipital articulation, and the opening or 

 foramen between the two occipital condyles 

 through which the spinal column is prolonged 

 into the cranial cavity so as to become con- 

 tinuous with the brain-mass. From the 

 posterior surface of the skull, where this 

 foramen is found in the lower Simiae, it 

 moves gradually down in the higher species 

 till at last it comes to occupy in man the 

 middle of the base of the skull. 



Anatomists are now agreed upon this, that 

 the brain of the Simiae is constructed exactly 

 on the same plan as that of man, that no part 

 is wanting to the former which is present in 



the latter; that the fissures which intersect 

 the brain-mass and the lobes and convolutions 

 lying between them are absolutely identical, 

 and are distinguished only in this, that their 

 forms become in man all the more complicated 

 the larger the mass becomes, besides which 

 the greater or smaller relative importance of 

 individual lobes and fissures must also be 

 taken into account. But in this case also the 

 gradual development, both from infancy to 

 the adult condition, and also from race to race 

 or species to species, can be demonstrated, 

 and the observation that the structural dif- 

 ferences between the brain of the anthropoid 

 apes and that of the lowest races of man are 

 much less than those which we meet with 

 in descending from the higher to the lower 

 Simiae, can no longer be shaken. 



The weight and volume of the brain of the 

 adult gorilla, the largest of the anthropoid apes, 

 only slightly exceed those of the brain of the 

 new-born (human) child. If only this circum- 

 stance be taken into consideration, other finer 

 specific differences being left out of account, 

 then we. may have some warrant for saying, 

 that the brain of the anthropoid apes only 

 when fully grown attains that degree of de- 

 velopment which the brain of the child pos- 

 sesses on its entrance into the world. 



No doubt, however, the anthropoid type of 

 brain structure is shown also in this, that in 

 all the Simiee, even the lowest, the cerebral 

 hemispheres are sufficiently developed to 

 overarch all the other parts, corpora quadri- 

 gemina and cerebellum, in such a manner that 

 when the brain is seen from above these are 

 completely covered. 



The three higher organs of sense, eye, nose, 

 and ear, are formed and situated exactly as in 

 the human child. The eyes are placed near 

 one another, separated only by a narrow nasal 

 ridge, and are set in completely closed capsu- 

 lar orbits in the front of the face. The nose 

 is flat as in the child, not prominent, the nos- 

 trils in some cases directed more sidewards 

 than forwards, more so than even in the 



