576 



My object at present, however, is not to explain the causes but 

 merely to place on record the fact of the frequent asymmetry of 

 the occipital poles of the cerebral hemispheres and its influence 

 on the form of the occipital bone and on the direction of the venous 

 sinuses. 



In the accompanying diagrams I have represented the condition 

 found in the occipital region of the brain, the cerebral sinuses and in 

 the occipital bone in almost 80" of Egyptians. A similar state of 

 affairs is found in about the some proportion of cases in the occipital 

 bone of ancient Egyptians of all periods from the earliest known pre- 

 historic times onward. 



The area striata (Fig. 1) extends far outward (often as much as 

 3 or even 4 centimetres) on to the caudal aspect of the left hemi- 

 sphere where it stops either exactly at or within a few millimetres 

 of the lip of the sulcus lunatus (s. simialis). Within this area there 

 is a longitudinal folding to form the sulcus calcarinus externus of 

 Cunningham (sulcus intrastriatus laterahs). 



On the right side the area striata barely crosses the edge of the 

 hemisphere so that the small sulcus lunatus is placed far back near 

 the extreme pole of the hemisphere and there is no sulcus calcarinus 

 externus, seeing that the homologue of the district which on the left 

 hemisphere forms its walls is on the right side placed on the mesial 

 surface, where it is folded perhaps in quite another manner to form a 

 part of the posterior calcarine sulcus or in other cases the so-called 

 "fissura extrema of Seitz". 



As a rule this lateral part of the area striata is on a different 

 plane to the rest of the surface of the occipital region, as though it 

 were a mushroom-like cake placed upon the surface. Hence the caudal 

 pole of the left hemisphere projects much further backward in such 

 cases than that of the right and a distinct depression is formed within 

 the superior (cerebral) fossa of the squama occipitalis. This might be 

 called the "fossa corticis striata e" (Fig. 2). Corresponding to 

 this inner depression there is in such cases, a marked projection of 

 the external surface of the left side of the occipital bone, such as 

 Tedeschi has described (op. cit. supra). 



In most Egyptian crania (of every period of Egyptian history at 

 present known) it is quite common to find the whole occipital squama 

 markedly bombe (Fig. 3); and the projecting part is almost in- 

 variably asymmetrical. The more prominent left swelling in such 

 cases is usually the direct result of the moulding of the plastic occi- 

 pital squama over the boss of area striata. 



