390 PROF. G. ELLIOT SMITH OX THE 



Alongside these remarkable statements we roiglit place Flower's comment concerning 

 "the absence of anything reseinl)ling the calcarine fissure [in the Cat's brain]" 

 (Trans. Zool. Soc. vol. v. p. 109). Flower's failure to recognize the identity of the 

 calcarine and splenial sulci is perhaps the more imintelligible, because he admits [mde 

 .supra) that a patent posterior cormi is not a condition absolutely necessary for the 

 existence of a calcar and a calcarine sulcus. 



In his earlier work on the Seal's T)rMin *, Sir W. Turner suggests homology between 

 the collateral sulcus of the Primates and splenial sulcus of " Q,uadrupeds " ; and, if 

 I read aright the memoir quoted above (Journ. Anat. and Pliys. a'oI. xxv.), the 

 splenial sidcus may be represented in the Primates by both the calloso-marginal and 

 collateral sulci. In comparison with the calcarine, these two furrows (calloso-marginal 

 and collateral) are of very minor importance f. 



Many other writers might be quoted to show the conflicting views whicb are put 

 forward to exj^lain the morphology of the splenial sulcus on the one band and the 

 calloso-marginal, calcarine, and collateral on the other. It will, however, suffice for our 

 purpose if we consider cbiefly the views of two modern writers, whose views are 

 diametrically opposed, the one to the other. Professor Ziehen finds in the Primate brain 

 some representative of almost CA^ery sulcus of the common mammalian brains ; whereas 

 Professor Cunningham adopts the extremist view expressed in his statement that, 

 " excejit in the case of certain of the main furrows {e. ff. Sylvian J, hippocampal), it is 

 very questionable indeed if there is any homological corres2)ondence between the sulci 

 of a primate brain and the sulci of a quadrupedal ])raiu." These remarks, written 

 several years ago, have been confirmed as lecently as this year, at the meeting of the 

 British Association. 



Ziehen lias discussed the representation of the calcarine sulcus among the general body 

 of mammals in several of his memoirs; but we shall chiefly consider the remarks in his 

 memoir on the Prosimiau brain § as being most pertinent to this discussion. In his 

 description of the " calcarine group " of furrows in Nycficehus, he says that the retro- 

 calcarine sulcus (whicii he labels o) is undoubtedly the calcai'ine fissure; and the calcarine 



* ' Challenger ' Reports. 



t Coiicerniug the latter sulcus Alex. Hill gives utterance to a eharacteristie remark : — " There is no doubt in m)^ 

 mind as to the horaolog)' of the ectorhinal [rhinal] fissure of the Dog with the collateral lissure in Man. ... To use 

 any other term than collateral fissure appears to me pedantic" ("The Hippocampus," Phil. Trans. 1893, p. 408). 

 As the rhinal fi.ssure is one of the iew furrows which can certainly be recognized by the histological features of its 

 lip.s, we can with certainty state, even if we are thereby stigmatized as pedantic by Dr. Hill, that the rhiual fissure 

 is not the collateral sulcu.s. 



One is surprised to find so cautious a writer as I^rofessor D. J. Cunningliam apparently subscribing to the same 

 view ; for he makes the statement that the " incisvra temporalis [i. e., a remnant of the rhinal fissure] . . . may be 

 regarded as a forward prolongation of the collateral fissure'' ('Manual of Practical Anatomy,' vol. ii. 189G, p. 501). 

 'i'his error is probably to bo explained by the fact that the jiart of the rhinal fissure which is on the caudal side of 

 (he incisura temporalis is commonly regarded by Human Anatomists (who disregard the distinction between the 

 jjyriform lobe and the neopallium in the so-called uncinate gyrus) as part of the collateral sulcus. 



J The case of the >Sylvian is rather unfortunate, as will be seen later, for the sulcus called '• Sylvian '' in the 

 ■■ (Quadrupeds '" is ceiiaiiihj nut the homologuo of the Primate " Sylvian fissure." 



§ Archiv f. Psychiat. lid. x.xviii. 181J0, p. OOiJ. 



