MOKPHOLOGY OF THE BEAIX IX THE :\[A:\r:\r.\LTA. 409 



Among Clark's conclusions it is slated tliat " the ckuslrum may iiiclud'' parts of areas 

 other than the insula " (p. 91), /. e. it may exleiid beyond tlie situations of the limit int;- 

 sulci. 



The most revolutionary and novel sugg'ostion in the foregoing discussion is the 

 homology of the suprasylvian sulcus of mammals in general partly with the superior 

 limiting sulcus and partly -with the ujjper (or posterior) part of the Sylvian li>sure of tho 

 Lemurs and Apes. 



Such an interpi elation of the morphology of the cerebral sulci has never been 

 suggested hitherto; and yet I belies-e that, if the identity of these two sulci be (h-nied, 

 it is impossible to homologizc the majority of the sulci in the brain of the i'rimates witli 

 those of other mammals. For if the furrow which is deepest, most stable, and most 

 precocious in the Carnivora, Ungulata, and Edentata is not represented in the Primates, 

 and, moreover, l)y that i)articular sulcus which is also most constant and develops 

 earliest, then it is utterly futile to seek for the homologues of the other uu)re varial)l(! 

 sulci. 



The only -writer (Ziehen) who has seriously attempted to homologizc the Prosimiau 

 sulci Avith those of other mammals [or, more strictly, with those of the Carnivora], found 

 representatives in the Primate brain for the lateral, coronal, an.sate, crucial, presylvitm, 

 ectolateral, medilateral, intraorbital, and postsylvian [his " fissura suprasylvia posterior'"] 

 of the Caruivora, and yet imagined that the most stable and deepest sulcus cf the; 

 Carnivora — the suprasylvian sulcus * — was missing when so many unimportant sulci are 

 reproduced. Such a suggestion is utterly inconceivable ; and, even if we knew nothing 

 of the instructive phenomena exhibited in Chimmijs,'n\ Myrmecophaga, and in Doltchoti.s, 

 the conclusion must be forced upon us that either the suprasylvian sulcus is merged in. 

 the Sylvian complex, or it is impossible to institute exact comparisons between the sulci 

 of the Primates and any other mammals. 



It is quite unnecessary to point out the fallacy of the old teaching of Pansch and 

 Meynert, that the suprasylvian sulcus represents the intraparietal sulcus of the 

 I'rimates. 



Several writers have ai)preciated the oljstruction in the way of a saiisfactory interpre- 

 tation of this region ; but I believe no one has hitherto suggested the solution which all 

 impartial observers must admit to be true. 



Thirty years ago Gervais saw the diihculty, ^ihen he wrote :—" Lemurs never have 

 more than two convolntidns around the Sylvian fissure, whilst even the smallest 

 Carnivores have three " f ; but did not explain which of the Carnivore furrows disguised 

 its identity by merging in another sulcus. 



Quite recently Holl recognized that the " Sylvian lissure " of Lemnr is composel of 

 two separate sulci ; but he suggested the ectosylvian, and not the suprasylvian, as the 

 dorsal element %. 



* Ziehen (Arch. f. Psych. Bd. xxviii.) says :—'• Dor vonkre Eogcnsabschnht dcr F. suprasylvia [/. ^. the true 

 sulcus supr^svlvius] fehlt dem Halhaffrngi-hiru " (p. 021). 



t Journ. a; Zoologie, tome i. p. 27. t Arch. f. Anat. u. Phys., A„at. Ahth. U.OO. 



59* 



