654 THE DEVELOPMENT oF SKULL AND BRAINS. 



opponents, it is only recently that thoir variations have been carefully 

 investigated. 



The frontal sinuses are usually supposed to vary according to 

 the degree of prominence of the glabella and the supraorbital 

 arches. This, however, is not the case. Thus Schwalbe" has figurcnl 

 a skull ill which the sinuses do not project as high as the top of 

 the glabella and supraor))ital prominences, and another in which 

 they extend considerably at)ove these projections. Further, Dr. 

 Logan Turner,'' who has made an extensive investigation into these 

 cavities, has shown that in the at)original 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 tlu^ frontal 

 sinuses do not usually reach above the glal)ella. Dr. Logan Turner, 

 however, foiuid that out of 174 skulls in which the frontal sinuses were 

 present, in i:)<> the simises extended above the ophryon. In 71 skulls 

 the depth of the sinus at the level of the ophryon varied from 2 to 1») 

 millimeters, the avei-age ])eing i'>.'2 millimeters, while in the same series 

 of skulls the depth at the glalxdla varied from ?> to 18 millimeters, with 

 an average dei)th of S.;") millimeters. 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 ])ased 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 reli- 

 ance upon this method are especially marked in the case of the study 

 of the pi-ehistoric 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 

 l)oints 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 )>rachy- 

 cephalic. T^et us take as an illustration an extreme case, such as the 

 skull of an adult male gorilla. Its glabella and supraorbital arches 

 will be found to project forward, its zygomatic arches outward, and 

 its transverse occipital crests backward far beyond the anterior, 

 lateral, and posterior limits of the cranial cavity. These outgrowths 

 are obviously correlated with the enormous development of the mus- 

 cles of mastication and those of the back of the neck. In a specimen 



" ' ' Studien iiber Pithecanthropus erectus, ' ' Zeitschrift f (ir Morphologie und Anthro- 

 pologie, Bd. i., 1899. 



''The Accessory Sinus^fs of the Xoi«e, 1901. 



