542 



NA TURE 



[October i, 1903 



The frontal sinuses are usually supposed to vary accord- 

 ing to the degree of prominence of the glabella and the 

 supra-orbital arches., This, however, is not the case. 

 Thus Schwalbe ' has figured a skull in which the sinuses 

 dp not project as high as the top of the glabella and supra- 

 orbital prominences, and another in which they extend con- 

 siderably above these projections. Further, Dr. Logan 

 Turner (" The Accessory Sinuses of the Nose," 1901), who 

 haj made an extensive investigation into these cavities, has 

 shown that in the aboriginal Australian, in which this 

 region of the skull is unusually prominent, the frontal 

 sinuses are frequently either absent or rudimentary.. The 

 ophryon has been selected by some craniologists as the 

 anterior point from which to measure the length of the 

 skull, under the impression that the frontal sinuses do not 

 usually reach above the glabella. Dr. Logan Turner, how- 

 ever, found that out of 174 skulls in which the frontal 

 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 16 mm., 

 the average being 52 mm., while in the same series of 

 skulls the depth at the glabella varied from 3 mm. to 

 18 mm., with an average depth of 85 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 the 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 Trinil and the 

 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, they will furnish you with 

 tables of measurements showing that one and the same 

 skull is dolichocephalic, mesaticephalic, 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 forwards, its zygo- 

 matic arches 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 the back of the neck. 

 In a specimen in my possession the greatest length of the 

 cranium, i.e. from glabella to external occipital protuber- 

 ance, is 195 mm., and the greatest breadth, taken between 

 the outer surfaces of the zygomatic processes of the tem- 

 poral 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 line 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 160 mm. by selecting the base of the protuber- 

 ance in place of its posterior extremity as the posterior end 

 measurement. This raises the index to 7375, 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 the 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. Accord- 

 ingly the glabella cannot be selected as the anterior point 

 from which to measure the length of the cranium, and 



1 " Studien fiber Pithecanthropus erectus" Zeitschrift fiir Morphologic 

 vnd Anthropologie, Ed. i. 1899. 



NO. 1770, VOL. 68] 



must, like the zygomatic arches and occipital protuberance, 

 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 justly urged against the glabella. Schwalbe 

 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 

 point either difficult to determine or 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 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 considered 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. 



I would suggest a spot in the median line of the supra- 

 glabellar fossa which is crossed by a transverse line uniting 

 the posterior borders of the external angular processes of 

 the frontal bone. I admit this plan is not free from objec- 

 tions, 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 25 mm., thus reducing it to 137 mm. The breadth being 

 calculated at 114 mm., the index is 8321, and hence dis- 

 tinctly brachycephalic. The length of the cranial cavity 

 is 118 mm. and the breadth 96 mm., and the length-breadth 

 index is thus the brachycephalic one of 81-36. 



I have given these somewhat detailed references to the 

 measurements 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, in order 

 to determine from external measurements the proportions 

 of the cranial cavity, skull outgrowths due to other factors 

 than brain growth must be rigorously excluded. Further, 

 these details will serve to emphasise the interesting fact 

 that the gorilla's skull is decidedly brachycephalic. This 

 character is by no means restricted to the gorilla, for it 

 has been clearly proved by Virchow, Schwalbe, and others 

 that all the anthropoid apes are markedly rcund-headed. 

 F-ver since the introduction by the illustrious Swedish 

 anthropologist Anders Retzius of a classification of skulls 

 according to the proportions between their length and 

 breadth great attention has been paid to this peculiarity 

 in different races of mankind. It has been generally held 

 that brachycephaly indicates a higher type of skull than 

 dolichocephaly, and that the increase in the size of the 

 brain in the higher races has tended to produce a brachy- 

 cephalic skull. When the cranial walls are subject to 

 excessive internal pressure, as in hydrocephalus, the skull 

 tends to become distinctly brachycephalic, as a given ex- 

 tent of wall gives a greater internal cavity in a spherical 

 than an oval form. In estimating the value of this theory 

 as to the evolutionary line upon which the skull has 

 travelled, 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 

 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 especially 

 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 " Trinil " skull-caps. According 

 to some authorities both these skull-caps are undoubtedly 

 human, while others hold that the " Neanderthal " belongs 

 to an extinct species of the genus Homo, and the " Trinil " 

 is the remains of an extinct genus — Pithecanthropus erectus 

 of Duboi — intermediate between man and the anthropoids. 

 One of ,.e most obvious and easily recognised peculiarities 

 of thest skull-caps is the very marked prominence of the 

 supra-orbital arches. The glabella-occipital length of the 



