Aly | 
524 THE NERVOUS SYSTEM. 
surface. The second deep annectant gyrus, termed the anterior cuneo-lingual, crosses the bottom 
of the calearine fissure a short distance behind the point where it is joined by the parieto-occi- 
pital fissure, and divides it into an anterior and a posterior part. The anterior calcarine fissure is 
slightly longer and much deeper than the posterior part. It includes the whole of the stem of 
Cuneus 
Callosal gyrus 
Corpus callosum 
Parieto-occipital fissure — 
_____ Optic thalamus 
Gyrus cuneus 
Cuneus 
Anterior cuneo- 
lingual gyrus 
Posterior calcarine 
fissure 
Posterior cuneo- 
lingual gyrus 
Anterior calearine 
fissure 
__Gyrus lingualis 
Collateral fissure 
Fic. 389.—INTERNAL PARIBTO-OCCIPITAL AND THE CALCARINE FISSURES FULLY OPENED UP, so as to show the 
deep annectant gyri marking off the several elements of the <-shaped system. 
the Y-shaped fissural arrangement and extends backwards for a short distance into the cuneus. 
It is the complete part of the fissure and gives rise to an elevation on the inner wall of the 
posterior horn of the lateral ventricle, to which the name of calear avis or hippocampus minor is 
given. The posterior calcarine fissure is shallower and is usually interrupted by the third deep 
annectant gyrus, viz. the posterior cuneo-lingual ; this divides it into two parts, of which the 
Fic. 390.—DEVELOPMENT OF THE PARIETO-OCCIPITAL AND THE CALCARINE FISSURES. 
A, Mesial aspect of a left cerebral hemisphere of a foetus approaching the end of the fifth month of develop- 
ment ; B, Mesial aspect of a right cerebral hemisphere of a fcetus in the beginning of the seventh 
month of development. 
S.L. Septum lucidum. cl. Anterior calcarine fissure. 
f. Fornix. C 
U. Unceus. Gan 
g.d. Gyrus dentatus. c.a. Anterior collateral fissure. 
p-0. Parieto-occipital fissure. e.m. Mid-collateral fissure. 
: \ nwo parts of posterior calcarine fissure. 
hinder is little more than the bifurcated extremity of the fissure. Very frequently this deep 
gyrus reaches the surface, and then the hinder end of the suleus is completely cut off. The 
posterior calcarine fissure is not a complete fissure. 
When the manner in which the calearine fissure is developed is studied, the various appear- 
ances which come into view when the bottom of the adult fissure is inspected receive the fullest 
explanation. The anterior calearine fissure is formed very early as an infolding of the wall of 
a 
