794 REPORT— 1903. 



' ligamentum suspensorium ' for the brain. Such descriptions 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. The.se, however, are mainly the lower portions, 

 such as the mi'dulla oblongata and pons Varolii, which may be regarded as prolon- 

 gations 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 .«ystem, and lience need special protection. They 

 are not, however, concei'ned with the regulation of complicated voluntary movements, 

 the reception and storage of sensory impressions from lower centres, and the activity 

 of the various mental processes. The.^e functions we must associate with the 

 liigher parts of the brain, and especially with the convolutions of the cerebral 

 hemispheres. 



If a cast be taken of tlie cranial cavity and compared with the brain which had 

 previously been carefully hai'dened in xi/u before I'emoval, it will be found that tlie 

 cast not only corresponds in its general form to that of the brain, but shows a con- 

 siderable numljer of the cerebral fissures aud eomolutions. Tliis moulding of the 

 inner surface of tlie skull to the adjacent portions of the cerebral hemispheres 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 aud the fluid to accumulate over th& 

 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 conviilutinns is so small that from a cast of the cranial cavity 

 we can obtain not onl}' a good picture nf the general shape and size of the higher 

 parts of the brain, but also various details as to the convolutionary pattern. Thi.s 

 method has been applied with marked succe.ss to the determination of the charac- 

 ters of the brain in \arious fossil lemurs by Dr. For.syth JNlajor and Professor R. 

 Burckhardt, and Professor Gustav Schwalbo has made a large series of such casts 

 from liis craniological collection in Strassburg. The interesting observations by 

 Schwalbe ' on the arrangement of the ' impressiones digitatro ' 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 marlced prominence at the bas(; of the human skull, sepa- 

 rating the anterior from tlie middle fo.'^sa, fits into the deep cleft between the 

 frontal and tempoi'al 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 corresponding to the portion of the Sylvian fissure of 

 the brain separating the irontal and parietal lobes from the temjioral lobe. Further,- 

 there is a distinct depression for the lodgment of the inferior frontal convolution, 

 and a cast of the middle cranial fossa sliows the three external temporal convo- 

 lutions. 



We must now turn to the consideration of the relations of the outer surface of 

 the cranium to its inner surface and to the brain. This question has engaged the 

 attention of experts as well as the ' man in the street ' since the time of Gall and 

 Spnrzheim, and one might naturally suppose that the last word had been said on 

 the .subject. This, however, is far from being the c.a.se. All anatomists are agreed 

 tliat the es.sential function of the cranium is to form a box for the support and 

 protection of the brain, and it is generally conceded that during the processes of 

 development and growth the form of the cranium is modified 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 moulds 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 immediate environment. There are 

 probably periods of development when the form of the brain is modified by the 



' 'Ueber die Beziohungen zwischen Innenform und Aussenform des Schadels,' 

 Beutsclies ArcMv fur Miimclte Meclichi, 1902. 



