540 



NATURE 



[October i, 1903 



band of experimenters have revolutionised our knowledge 

 of the anatomy and physiology of the higher nerve centres. 



The value of the results thus obtained is greatly enhanced 

 by the consciousness that they bear the promise of still 

 greater advances in the near future. If the results obtained 

 by the craniologist have been less marked, this arises mainly 

 from the nature of the subject, and is certainly not due to 

 any lack of energy on their part. Our craniological collec- 

 tions are continually increasing, and the various prehistoric 

 skull-caps from the Neanderthal to the Trinil still form 

 the basis of interesting and valuable memoirs. 



While the additions to our general knowledge of cerebral 

 anatomy and physiology have been so striking, those aspects 

 of these subjects which are of special anthropological 

 interest have made comparatively slight progress, and can- 

 not compare in extent and importance with the advantages 

 based upon a study of fossil and recent crania. These facts 

 admit of a ready explanation. Brains of anthropological 

 interest are usually difficult to procure and to keep, and 

 require the use of special and complicated methods for their 

 satisfactory examination, while skulls of the leading races 

 of mankind are readily collected, preserved, and studied. 

 Hence it follows that the crania in our anthropological 

 collections are as numerous, well preserved, and varied as 

 the brains are few in number and defective, both in their 

 state of preservation and representative character. It may 

 reasonably be anticipated that improved methods of pre- 

 servation and the growing recognition on the part of 

 anthropologists, museum curators, and collectors of the 

 importance of a study of the brain itself will to some extent 

 at least remedy these defects ; but so far as prehistoric man 

 IS concerned, we can never hope to have any direct evidence 

 ..of the condition of his higher nerve centres, and must de- 

 pend for an estimate of his cerebral development upon those 

 'more or less perfect skulls which fortunately have resisted 

 .for so many ages the corroding hand of time. 



I presume we will all admit that the main value of a good 

 collection of human skulls depends upon the light which 

 they can be made to throw upon the relative development 

 of the brains of different races. Such collections possess 

 few, if any, brains taken from these or corresponding 

 skulls, and we are thus dependent upon the study of the 

 skulls alone for an estimate of brain development. 



Vigorous attacks have not unfrequently been made upon 

 the craniometric systems at present in general use, and 

 the elaborate tables, compiled with so much trouble, giving 

 the circumference, diameters, and corresponding indices of 

 various parts of the skull, are held to afford but little 

 information as to the real nature of skull variations, how- 

 ever useful they may be for purposes of classification. 

 While by no means prepared to express entire agreement 

 with these critics, I must admit that craniologists as a 

 whole have concentrated their attention mainly on the ex- 

 ternal contour of the skull, and have paid comparatively 

 little attention to the form of the cranial cavity. The outer 

 surface of the cranium presents features which are due 

 to other factors than brain development, and an examin- 

 ation of the cranial cavity not only gives us important in- 

 formation as to brain form, but by affording a comparison 

 between the external and internal surfaces of the cranial 

 wall it gives a valuable clue to the real significance of the 

 external configuration. Beyond determining its capacity 

 we can do but little towards an exact investigation of the 

 cranial cavity without making a section of the skull. 

 Forty years ago Prof. Huxley, in his work " On the 

 Evidence of Man's Place in Nature," showed the import- 

 ance of a comparison of the basal with the vaulted portion 

 of the skull, and maintained that until it should become 

 " an opprobrium to an ethnological collection to possess a 

 single skull which is not bisected longitudinally " there 

 would be "no safe basis for that ethnological craniology 

 which aspires to give the anatomical characters of the 

 crania of the different races of mankind." Prof. Cleland 

 and Sir William Turner have also insisted upon this method 

 of examination, and only two years ago Prof. D. J. 

 Cunningham, in his Presidential Address to this Section, 

 quoted, with approval, the forcible language of Huxley. 

 The curators of craniological collections appear, however, 

 to possess an invincible objection to any such treatment 

 of the specimens under their care. Even in the Hunterian 

 Museum in London, where Huxley himself worked at this 

 subject, among several thousands of skulls, scarcely any 



ro. 1770, VOL 68] 



have been bisected longitudinally, or had the cranial cavity 

 exposed by a. section in any other direction. The method 

 advocated so strongly by Huxley is not only essential to a 

 thorough study of the relations of basi-cranial axis to the 

 vault of the cranium and to the facial portion of the skull, 

 but also permits of casts being taken of the cranial cavity ; 

 a procedure which, I would venture to suggest, has been 

 too much neglected by craniologists. 



Every student of anatomy is familiar with the finger-like 

 depressions on the inner surface of the cranial wall, which 

 are described as the impress of the cerebral convolutions ; 

 but their exact distribution and the degree to which they 

 are developed according to age, sex, race, &c., still remain 

 to be definitely determined. Indeed, there appears to be a 

 considerable difference of opinion as to the degree of 

 approximation of the outer surface of the brain to the inner 

 surface of the cranial wall. Thus the brain is frequently 

 described as lying upon a water-bed, or as swimming in 

 the cerebro-spinal fluid, while Hyrtle speaks of this fluid as 

 a " ligamentum suspensorium " for the brain. Such de- 

 scriptions are misleading when applied to the relation of 

 the cerebral convolutions to the skull. There are, it is 

 true, certain parts of the brain which are surrounded and 

 separated from the skull by a considerable amount of fluid. 

 These, however, are mainly the lower portions, such as the 

 medulla oblongata and pons Varolii, which may be regarded 

 as prolongations of the spinal cord into the cranial cavity. 

 As they contain the centres controlling the action of the 

 circulatory and respiratory organs, they are the most vital 

 parts of the central nervous system, and hence need special 

 protection. They are not, however, concerned with the 

 regulation of complicated voluntary movements, the recep- 

 tion and storage of sensory impressions from lower centres, 

 and the activity of the various mental processes. These 

 functions we must associate with the higher parts of the 

 brain, and especially with the convolutions of the cerebral 

 hemispheres. 



If a cast be taken of the cranial cavity and compared 

 with the brain which had previously been carefully hardened 

 in situ before removal, it will be found that the cast not 

 only corresponds in its general form to that of the brain, 

 but shows a considerable number of the cerebral fissures 

 and convolutions. This moulding of the inner surface of 

 the skull to the adjacent portions of the cerebral hemi- 

 spheres is usually much more marked at the base and sides 

 than over the vault. Since the specific gravity of the brain 

 tissue is higher than that of the cerebro-spinal fluid, the 

 cerebrum tends to sink towards the base and the fluid to 

 accumulate over the vault ; hence probably these differences 

 admit of a simple mechanical explanation. Except under 

 abnormal conditions, the amount of cerebro-spinal fluid 

 between the skull and the cerebral convolutions is so small 

 that from a cast of the cranial cavity we can obtain not 

 only a good picture of the general shape and size of the 

 higher parts of the brain, but also various details as to 

 the convolutionary pattern. This method has been applied 

 with marked success to the determination of the characters 

 of the brain in various fossil lemurs by Dr. Forsyth Major 

 and Prof. R. Burckhardt, and Prof. Gustav Schwalbe has 

 made a large series of such casts from his craniological 

 collection in Strassburg. The interesting observations by 

 Schwalbe' on the arrangement of the " impressiones 

 digitatae " and " juga cerebralia," and their relation to 

 the cerebral convolutions in man, the apes, and various 

 other mammals, have directed special attention to a very 

 interesting field of inquiry. As is well known, the marked 

 prominence at the base of the human skull, separating the 

 anterior from the middle fossa, fits into the deep cleft 

 between the frontal and temporal lobes of the brain, and 

 Schwalbe has shown that this ridge is continued — of course 

 in a much less marked form — along the inner surface of 

 the lateral wall of the skull, so that a cast of the cranial 

 cavity presents a shallow but easily recognised groove corre- 

 sponding to the portion of the Sylvian fissure of the brain 

 separating the frontal and parietal lobes from the temporal 

 lobe. Further, there is a distinct depression for the lodg- 

 ment of the inferior frontal convolution, and a cast of the 

 middle cranial fossa shows the three external temporal 

 convolutions. 



We must now turn to the consideration of the relations 

 1 " Ueber die Beziehungen zwischen Innenform und Aussenform des 

 Schadels," Deutsches Archiv fur klinische Medicin, 1902. 



