62 PROCEEDINGS OP THE ACADEMY OF [1879. 



bits the upper, middle, and lower frontal convolutions, 1 separated 

 by the upper and lower frontal fissure, the latter passing into the 

 vertical frontal (precenti'al). The central fissure (Rolando) is 

 well marked, a little more forward in the Chimpanzee than in 

 Man, separating the anterior and posterior central convolutions. 

 The fissure of Sylvius is in such relation with the interparietal 

 and temporal fissures, that the supra-marginal and angular 

 convolutions are identical with those of Man. The "ascending: 

 branch" of the Sylvian fissure also passes in between the middle 

 frontal and precentral fissures as in Man. The first, second, and 

 third temporal convolutions, with the first and second temporal 

 fissures, are as distinct in the Chimpanzee as in Man, and the con- 

 tinuity of the occipital and temporal lobes through the lower 

 temporal convolutions (3d and 4th plis de passage of Gratiolet) 

 is as unbroken' in our ape as in the human being. Further, the 

 three convolutions of the occipital lobe, with its transverse occipi- 

 tal and inferior longitudinal fissures, do not present any very 

 marked differences from the homologous structure in Man. Up to 

 this point I believe I have made no statements in reference to the 

 fissures and convolutions of the brain of the Chimpanzee which 

 have not been substantially made before. There has, however, 

 been, and is still, a diversity of opinion in reference to the parts 

 of the occipital convolutions which bridge over the external per- 

 pendicular fissure, which seems to be a continuation of the internal 

 perpendicular or parieto-occipital fissure. The convolutions which 

 I have referred to above as the upper and middle occipital convo- 

 lutions pass in Man and Ateles so insensibly into the upper parietal 

 lobule and angular convolutions respectively that apparently no 

 external perpendicular fissure exists ; the parieto-occipital, how- 

 ever, being apparent enough. In the Chimpanzee that I dissected, 

 the external perpendicular fissure is quite apparent, but the two 

 occipital convolutions seem to me to be present, the upper one 

 serving to partially bridge over the inner part of the external per- 

 pendicular fissure connecting the upper occipital with the upper 

 parietal lobule, the middle occipital passing into the angular con- 

 volution and bridging over the outer part of the external perpen- 

 dicular fissure; the difference then in the brain of the Chimpan- 

 zee and Man in this respect being one essentially of degree, the 



1 I make use of the nomenclature of Ecker in " Cerebral Convolutions of 

 Man," English synonymes. 



