THE DEVELOPMKTSTT OK SKTLL AND BRAINS. fi51 



question has engaged the attention of experts as well as the ""man in 

 the street" since the time of Gall and Spurzheim, and one might 

 naturally suppose that the last word had been said on the subject. 

 This, however, is far from being* the case. All anatomists are agreed 

 that the essential function of the cranium is to form a box for the su} - 

 port and protection of the brain, and it is generally conceded tluu 

 during- the processes of development and growth the form of th(> 

 cranium is moditied in response to the stimulus transmitted to it by 

 the brain. In fact, it is brain growth that determines the form of the 

 cranium, and not the skull that molds the brain into shape. This 

 belief, however, need not be accepted without some reservations. 

 Even the brain may be conceived as being influenced by its inmiediate 

 environment. There are probably periods of development when the 

 form of the brain is moditied b}^ the resistance offered by its cover- 

 ings, and there are certainly stages when the brain does not full}^ 

 occupy the cranial cavity. 



At an early })eriod in the phylogeny of the vertebrate skull the 

 structure of the greater part of the cranial wall chang'es from mem- 

 branous tissu(» into cartilage, tho portion persisting as membrane 

 being situated near the median dorsal line. In the higher vertebrates 

 the rapid and early expansion of the dorsal part of the forebrain is so 

 marked that tiie cartilaginous growth fails to keep pace with it, and 

 more and more of the dorsal wall of tlu^ ci"aniuni remains membranous, 

 and subseciuently ossifies to form membrane bones. C^artilage, tiiough 

 constituting a firmer support to the brain than membrane, does not 

 possess the same capacity of rapid growth and expansion. The head 

 of a 3'oung child is relatively large, and its skull is distinguished from 

 that of an adult by the small size of the cartilaginous base of the 

 cranium as compared with the membranous vault. The appearance of 

 topheaviness in the young skull is gradually obliterated as age advances 

 by the cartilage continuing slowly to grow after the vault has practi- 

 call}" ceased to enlarge. These changes in the shape of the cranium 

 are associated with corresponding alterations in that of the brain, and 

 it appears to me that we have here an illustration of how the conditions 

 of skull gi-owth may modify the general form of the brain. 



Whatever may be the precise infiu(mces that determine skull and 

 brain growth, there can I)e no dou))t but that within certain limits the 

 external form of the cranium serves as a reliable guide to the shape of 

 the brain. Statements such as those \)y Dr. J. Deniker," "that the 

 inequalities of the external table of the cranial walls have no relation 

 whatever with the irregularitiivs of the inner table, and still less have 

 anything in common with the configuration of the various parts of the 

 brain," are of too general and sweeping a character. Indeed, various 

 observers have drawn attention to the fact that in certain regions the 



«Tfie Races of Man, p. 53. 



