328 N. W. INGALLS 



nicke, or the ramus ascendens sulci temporalis medii of human 

 anatomy. 



The region below the interparietal is more difficult to deal with 

 in the higher Anthropoids on account of the greater complexity 

 both as regards areas and sulci. The factors involved are an in- 

 crease and further differentiation of this part of the parietal area 

 and to a less extent, similar changes in the preoccipital area with 

 the effect of their increased growth upon the areas and fissures 

 of the temporal region. On account of the changes in areas 7, the 

 Sylvian and parallel sulci have been forced downward and ren- 

 dered more horizontal. The complexity of the posterior ends of 

 these fissures has been heightened, being usually expressed in 

 bifurcations or an increase in the foldings in the neighborhood 

 or by confluence with them. This applies especially to the parallel 

 sulcus and with it the anterior occipital which to a certain extent 

 is compensatory, or one might say vicarious, in character. 



With an area of constant extent it is obvious that the effect 

 of increased folding will be to lessen its dimensions, as seen on 

 the surface, and further to vary to a certain degree, its location. 

 The common, deep posterior or descending branch of the Sylvian 

 is sufficient to accommodate within itself the posterior part of 

 area 22, which is not only slowly decreasing in size but is in ad- 

 dition being crowded downward by area 7 and this branch will 

 then appear as the boundary between these two areas. This 

 process of infolding would have materially shortened the main 

 stem of the Sylvian were an increase in length not necessitated 

 by the increase in area 7 or brought about by its union with already 

 existent furrows, but this new end of the Sylvian, in cases in which 

 it is present, turns sharply upward as a rule and lies, not between 

 7 and 22, but within 7 and therefore we have termed it new. This 

 ramus ascendens is an axial furrow, which may however be sepa- 

 rate and occupy varying positions or be associated with other 

 furrows which could be termed axial since they occur within a defi- 

 nite area. The anterior occipital occurs more often as an inde- 

 pendent, well developed sulcus in the higher Simiidae. The newer 

 sulci which come into relation with the parallel sulcus are either 



