TRANSACTIONS OF SECTION H. 797 



been selected by some craniologists as tlie anterior point from which to measure 

 the- leuf^th of the skull, inider the impression that the frontal sinuses do not 

 uaually reach above the olabolla. Dr. Logan Turner, however, found that out of 

 174 skulls in which the Irontal sinuses were present in 130 the sinuses extended 

 above the ophryon. In seventy-one skulls the depth of the sinus at the level of 

 the ophryon varied from 2 mm. to 1(3 mm., the averaf^e being ry2 mm., while in 

 the same series of skulls tiie depth at the glabella varied from 3 mm. to 18 mm., 

 with an average depth of 8'5 mm. It thus appears that the selection of the ophryon 

 in preference to the glabella, as giving a more accurate clue to the length of the 

 brain, is based upon erroneous assumptions, and that neither point can be relied 

 upon in the determination of the anterior limit of the cranial cavity. 



The difficulties of estimating tlie extent of the cranial cavity by external 

 measurements and the fallacies that may result from a reliance upon this method 

 are especially marked in the case of the study of the prehistoric human calvaria, 

 such as the Neanderthal and the Tiiuil and tlie skulls of the anthropoid apes. 



Statistics are popularly supposed to be capable of proving almost anything, 

 and certainly if you allow craniologists to select their own points from which to 

 measure the length and breadth of the cranium, tbey will furnish you with tables 

 of measurements showing that one and the same skull is dolichocephalic, mesati- 

 cephalic, and brachycephalic. Let us take as an illustration an extreme case, such 

 as the skull of an adult male gorilla. Its glabella and supra-orbital arches will be 

 found to project I'orwards, its zygomatic arcings outwards, and its transverse 

 occipital crests backwards, far beyond the anterior, lateral, and posterior limits of 

 the cranial cavity. These outgrowths are obviously correlated with the enormous 

 development of the muscles of mastication and those of thr Ijack of the neck. In 

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

 to external occipital protuberance, is 195 mm., and the greatest breadth, taken 

 between the outer surfaces of the zygomatic processes of the temporal bone, is 

 172 mm., giving the marked brachycephalic index of 88-21. The zygomatic 

 processes, however, may reasonably be objected to as indicating the true breadth, 

 and the side wall of the cranium just above the liny where the root of this process 

 springs from the squamous portion of the temporal bone will certainly be much 

 nearer the cranial cavity. Measured in this situation the breadth of the cranium 

 is 118 mm., which gives a length-breadth index 60'51, and thus represents the 

 skull as decidedly dolichocephalic. The transverse occipital crests and the point 

 where these meet in the middle line to form 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 IGO mm. 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 mesaticephalic group. At the anterior part of the skull the 

 prominent glabella is separated from the inner table of the skull by large air 

 sinuses, so that on a median section of the skull the distance from the glabella to 

 tlie nearest part of the cranial cavity is 36 mm. 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 

 cannot be selected as the anterior point from which to measure tbe length of the 

 cranium, and must, like the zygomatic arches and occipital protuberance, be 

 excluded from our calculations it we desire to determine a true length-breadth 

 index. The difficulty, however, is to select a delinite point on the surface of the 

 cranium to repi-esent its anterior end, which will be free from the objections justly 

 urged against the glabella. 8chwalbe suggests the hinder end of the supra- 

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

 less distinctly marked frontal crest. I have found this pohit either difficult to 

 determine or too far back. Thus in my mah' gorilla the posterior end of this fossa 

 formed by the meeting of the two temporal ridges was 50 mm. behind the glabella, 

 and only 24 mm. 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 supra-glabellar fossa. This point is 22 mm. 

 from the glabella, and between 50 mm. and 60 mm. in front of the bregma. 



