PARIETAL REGION IN THE PRIMATE BRAIN 337 



from the temporal area (i.e., their derivatives), while behind it 

 holds the same relations to the later differentiations of the pre- 

 occipital area. We may note here that in all human brains, even 

 the most primitive and pithecoid, the distance between the lunate 

 and superior temporal is always much greater than in any of the 

 anthropoids. The reason for this has already been made clear. 

 The superior temporal sulcus lies below a very productive area, 

 the growth of which would tend to increase the distance between 

 these two sulci. 



The anterior occipital, limiting the parieto-occipital area in 

 front, is more variable, since it is found in cortex that is, phylo- 

 genetically, very young. Its position will be largely influenced 

 by the relations of the ramus occipitalis and this in turn by the 

 peristriate area above it. It may be shifted downward in the same 

 way and for the same reason as the lunate especially if the par- 

 occipital is long. In extreme cases where the lunate has been 

 pushed down to the lateral border the anterior occipital sulcus may 

 be almost sagittally placed. It is usually found about opposite 

 the parieto-occipital and may, as in this case be united with the 

 temporo-parietal, or be independent. Frequently it is confluent 

 with the middle temporal particularly when it is situated further 

 forward. 



The inferior occipital is quite typical on both sides, and essen- 

 tially simian. It is the anterior and lateral boundary of the 

 temporo-occipital and peristriate areas. It is a rather variable 

 fissure: it may be found on the lateral or tentorial surface, its 

 anterior end particularly tends to turn rather abruptly upward, 

 which part may unite with the middle temporal, submerging in 

 part between them the paratemporal area, 37. If lower down it 

 can unite with the inferior temporal (temporo-occipital). Asso- 

 ciated as it is with the peristriate area and through this with the 

 striate its relations are closely connected with the condition of 

 the lunate. This and the anterior occipital sulcus not infrequently 

 unite to form a deep, vertical or curved fissure extending from the 

 lateral border of the hemisphere upward toward the parieto-oc- 

 cipital. In shape it may resemble a lunate. This condition would 



