NERVOUS SYSTEM. VERTEBBATA. 4Q5 



sulcus has extended far on to the dorsal surface, and has 

 become exceedingly deep. Not only so, but its walls ure 

 rendered very irregular by numerous sulci, one of which 

 emerges from the sulcus on the mesial surface of the left 

 hemisphere. With the presence of this deep sulcus there 

 is no need for a " compensatory " (Broca's " postlimbic") 

 sulcus : and all the less so because the calloso-marginal 

 sulcus approaches very near to the parieto-oceipital sulcus. 

 The unusually great dorsal extent of the parieto-occipital 

 sulcus greatly disturbs the intraparietal sulcus. The latter 

 consists of a triradiate arrangement far removed from the 

 mesial plane. One limb of the sulcus extends between the 

 upper ends of the Sylvian fissure and the parallel sulcus 

 (both of which are very short). A second limb appears to 



Fig. 240. (x.) 



SULC.PAR.OCC. ^ ____^ SULC.CALL.MARG. 



lie- <^sr ^-m^m ' SULC - GEI 



SULC.L.OCC. 



SULC.CALC. ^^jjjjjjjm- SULC.ROS7. 



SULC COLL. RHIN.F. 



join the mid-point of the Affenspalte, but in reality it runs 

 parallel to the upper half of the latter, separated from it by 

 a very deeply-submerged gyrus. The anterior limb of the 

 triradiate sulcus extends above the Sylvian fissure toward 

 the mid-point of the central gyrus. On the left hemisphere 

 it joins the ramus postcentralis superior, which is a separate 

 sulcus on the right side. 



The Simian sulcus (Affenspalte) is short but very deep, 

 and its posterior lip is slightly opercular. Behind its upper 

 end there is a short compensatory sulcus, such as is some- 

 times seen in Cebus. The inferior occipital sulcus approaches 

 very close to the caudal end of the collateral sulcus. An 

 obliquely directed lateral occipital sulcus (not hitherto met 

 with) crosses the hemisphere from the occipital pole to ward 

 tbe mid-point of the Simian sulcus (SULC. L. OCC.). 



