THE DEVELOPMENT OF SKULL AND BRAINS. 655 



in my possession the greatest length of the cranium, i. e., from glabella 

 to external occipital protuberance, is 195 millimeters, and the greatest 

 breadth, taken between the outer surfaces of the zygomatic processes 

 of the temporal bone, is 172 millimeters, giving the marked ])rachy- 

 cf^phalic index of 88.21. The zygomatic processes, however, may 

 reasonably be o})jected to as indicating the true breadth, and the side 

 wall of the cranium just a))ove the line where the root of this process 

 springs from the squamous portion of the temporal bone will certainly 

 ba much nearer the cranial cavit3\ Measured in this situation the 

 breadth of the cranium is 118 millimeters, which gives a length- breadth 

 index of 60.51, and thus represents the skull as decidedly dolichoce- 

 phalic. The transverse occipital crests and the point where these 

 meet in the middle line to foi'm the external occipital protuberance 

 are much more prominent in the male than in the female gorilla, and 

 the estimate of the length of the cranium in this male gorilla may be 

 reduced to 160 millimeters, by selecting the base of the protuberance 

 in place of its posterior extremity as the posterior end measurement. 

 This raises the index to 73.75, and places the skull near the mesati- 

 cephalic group. At the anterior part of the skull the prominent 

 glabella is sepai'ated from the inner table of the skull by large air 

 sinus(\s, so that on a median section of the skull the distance from 

 the glabella to the nearest part of the cranial cavity is 36 millimeters. 

 We have here, therefore, another outgrowth of the cranial wall which 

 in an examination of the external surface of the skull obscures the 

 extent of the cranial cavity. Accordingly the glabella can not be 

 selected as the anterior point from w^hich to measure the length of the 

 cranium, and must, like the zygomatic arches and occipital protuber- 

 ance, be excluded from our calculations if we desire to determine a 

 true length-breadth index. The difficulty, however, is to select a 

 definite point on the surface of the cranium to represent its anterior 

 end, which will be free from the objections justl}^ urged against the 

 glabella. Schwalbe suggests the hinder end of the supraglabellar 

 fossa, which he states often corresponds to the beginning of a more 

 or less distinctly marked frontal crest. I have found this point either 

 difficult to determine oi- too far back. Thus in my male gorilla the 

 posterior end of this fossa formed by the meeting of the two temporal 

 ridges was 56 millimeters ])ehind the glabella, and only 24 millimeters 

 from the bregma, while in the female gorilla the temporal ridges do 

 not meet, but there is a low median frontal ridge, which may be con- 

 sidered as bounding posteriorly the supraglabellar fossa. This point 

 is 22 millimeters from the glabella, and between .50 and 6o millimeters 

 in front of the bregma. 



I would suggest a spot in the median line of the supraglabellar 

 fossa which is crossed by a transverse line uniting the posterior bor- 



