MORPHOLOGY OF THE BRAIN IN THE MAMMALIA. 



389 



It is obvious, tlicrefore, that it is tlic rctrocalcariac aud not tlio true calcarine sulcus 

 whicli Broca has called " sillon calearin " in tlie brains of the Roebuck and Ass. The 



src. 



Cant eJ us </roiH(_(/{H-itts. 

 Mesial aspect of the right ctn'hrul hemisphere. Xat. size. 



true calcarine sulcus in these mammals is represented in a part of tlie great furrow 

 ^Ahich he calls " linii)ie." 



If my view of this matter be correct, most recent English writers have departed much 

 further from the true interpretation than even Ivrueg aud Eroca. 



In his well-know^n memoir " On the Convolutions of the Brain," Sir William Turner * 

 gave expression to very decided opinions concerning the calcarine sulcus and posterior 

 cornu. Writing about the l)rain of Hapnle Jacchns, he states : — "There is no splenial 

 tissvire, but ojiposite the splenium a distinct calcarine fissure " (p. 141). This amounts 

 to a categorical denial of the homology of the calcarine and splenial sulci. 



On the same page he makes the I'urther statement (in this case referring to the In'ain 

 of Nycticehiis 'iStenops\) that " the calcarine fissure . . . proves the jiresence of both 

 posterior cornu and calcar avis " f . The data upon which this statement is based are 

 borrowed from Flower (Phil. Trans. 1802), Avho says, in the memoir quoted, that he found 

 it impossible to determine in this particular brain "whether or not the posterior cornu 

 exists." Nevertheless Turner goes on to say that " if the surface of the hemisphere 

 be examined with the view of determining the presence of an occipital lobe by the 

 evidence of a fissure, the calcarine fissure is that which is to be regarded as of primary 

 importance" (p. ll'l). This means presumably that there is no "occipital lobe" in any 

 mammals other than the Primates, seeing that the " calcarine fissure" is supjjosed to be 

 absent. The splenial sulcus, which occupies the position of the calcarine sulcus, i=i 

 regarded by Turner as merely a part of the calloso-margiual sulcus (p. 111). 



* Joarn. Anat. and Phjs. vol. xxv. 1890. 



t I have shown in these notes that there is no posterior cornu in the hrain of Nyi-iirehus. 



