(i56 THE DEVELOPMiSNT OF SKULL AND BRAINS. 



ders of the external angular proce.sse.s of the frontal bone. 1 admit 

 this plan is not free from objections, but it possesses the advantages 

 of being available for both male and female skulls. In my male skull 

 the selection of this point diminishes the length of the cranium by 'iio 

 millimeters, thus reducing it to 137 millimeters. The breadth being 

 calculated at 114 millimeters the index is 83.21, and hence distinctly 

 brachycephalic. The length of the cranial cavity is 118 millimeters 

 and the breadth 90 millimeters, and the length- breadth index is thus 

 the brach3"cephalic one of 81.36. 



I have given these somewhat detailed references to the measure- 

 ments of this gorilla's skull because they show in a very clear and 

 obvious manner that from an external examination of the skull one 

 might easily be misled as to the size and form of the cranial cavity, 

 and that ii,i order to determine from external measurements the pro- 

 portions of the cranial cavity, skull outgrowths due to other factors 

 than brain growth must be rigorously excluded. Further, these 

 details will serve to eiiiphasize the interesting fact that the gorilla's 

 skull is decidedly brachycephalic. This character is by no means 

 restricted to the gorilla, for it has l)een clearly proved ))y Virchow. 

 Schwalbe, and others that all the anthropoid apes are markedly round- 

 headed. Ever since the introduction b}?^ the illustrious Swedish anthro- 

 pologist, Anders Ketzius, of a classification of skulls according to the 

 proportions between their length and breadth, great attention has 

 been paid to this peculiarit}'^ in different races of mankind. It has 

 l)een generally held that brachycephaly indicates a higher type of 

 skull than dolichocephaly, and that the increase in size of the brain in 

 the higher races has tended to produce a brachycephalic skull. When 

 the cranial walls are subject to excessive internal pressure, as in hydro- 

 cephalus, the skull tends to become distinctly brach3^cephalic, as a 

 given extent of wall gives a greater internal cavity in a spherical than 

 an oval form. In estimating the value of this theor}^ as to the evolu- 

 tionary line upon which tlie skull has traveled, it is obvious that the 

 brachycephalic character of the skulls of all the anthropoid apes is a 

 fact which requires consideration. 



Although an adult male gorilla, such as I have selected, presents 

 in an extreme degree outgrowths from the cranial wall masking the 

 true form of the cranial cavity, the same condition, though to a less 

 marked extent, is met with in with the human subject. Further, it is 

 interesting to note that the length of the skull is more liable to be 

 increased by such growths than the breadth, since they occur espe- 

 cially over the lower part of the forehead and to a less degree at the 

 back of the skull, while the side walls of the cranium in the region of 

 its greatest breadth generally remain thin. 



Few if any fossils have attracted an equal amount of attention or 

 given rise to such keen controversies as the " Neanderthal'" and the 



