Literary Notices. Hi 



peculiar to primates and appear prior to the appearance of a distinct 

 occipital lobe. 



The parieto-occipital and calcarine fissures form upon the mesal 

 aspect of a posterior part of the adult hemisphere a > — shaped figure. 

 The stem is directed obliquely ventrad and intersects the gyrus 

 fornicatus. The parieto-occiptal fissure forms the more direct contin- 

 uation of the stem and continues on the ectal surface as the external 

 parieto-occipital fissure. The calcarine branch passes toward the 

 occipital pole. The stem is called the anterior calcarine fissure. The 

 apex of the cuneus gives off two deep annectant gyri — the gyrus 

 cunei and anterior cuneo lingual gyrus. The gyrus cunei forms a bar- 

 rier between the parieto-occipital fissure and the stem, while the gyrus 

 cuneo-lingualis anterior separates the stem and the posterior part of 

 the calcarine fissure. 



The calcar (hippocampus minor) is formed wholly by the stem or 

 anterior calcarine fissure. 



In apes the calcarine fissure is deep and much more stable than 

 the parieto-occipital. In the chimpanzee the gyrus cuneus is on the 

 surface (a condition found in 3-9 per cent, of human brains) while in 

 the orang and gibbon the cunei may be on the surface or at the bot- 

 tom of the fissure. The gyrus cunei is never absent. Cunningham 

 believes that the whole calcarine fissure of anthropoids corresponds 

 to the "stem" of the human calcarine or rather the whole length of 

 the precursor of the human calcarine is the equivalent of the ape 

 calcarine. The posterior calcarine of man is of later origin and takes 

 the place of an abolished portion of the original fissure. The cuneus 

 of the ape does not have the same morphological value as that of man. 

 Only the cephalic part is present in the ape, the caudal part is absent 

 or blended with the gyrus lingualis. In the ape the entire length of 

 the calcarine fissure is on the tentorial face of the hemisphere. 



The posterior calcarine fissure is distinct from the "stem" in 

 origin, the latter being a "complete fissure" and having unbroken 

 continuity of existence with the fore-part precursor. 



The occipital and parietal indices are the distances along the mesal 

 margin of the hemisphere intercepted by the intersection of the ex- 

 ternal parieto-occipital fissure and the fissure of Rolando respectively, 

 in the firsc case measuring from the occipital pole, in the second, from 

 the parieto-occipital intersection, both these distances in terms of 

 hundredths of the entire length along the dorsal margin of the 

 hemisphere. 



