288 DAVIDSON BLACK 



the cerebral portion of the cast is 35 cc, that of the cerebeUiim 

 and brain stem being 13 cc. 



Brain stem and basis craiiii. (Fig. 13.) The ridge correspond- 

 ing to the internal carotid artery is indistinct on the right side 

 of this cast in the neighborhood of the foramen lacerum poste- 

 rior, though its fellow on the left presents relations similar to 

 those obtaining in Specimen II. No indication can be made out 

 of a transverse connection between these arterial ridges. 



The depression for the lodgement of the posterior clinoid proc- 

 esses is somewhat deeper than in Specimens I and II. An ill 

 defined transverse retro-pontal depression may be distinguished 

 and a short distance caudal to it a second similar depression 

 occurs. The latter is placed on a level with the caudal margins 

 of the internal auditory meati and possibly corresponds to the 

 inferior margin of the trapezoid body. The foregoing slight 

 irregularities on the basi-occipital surface of this specimen may 

 be felt distinctly with the finger tips, though they can only be 

 seen in oblique illumination. 



The site of the left precondylar foramen is well defined, but 

 on the right side the corresponding area is broken away. 



Cerebral hemispheres. In a dorsal view of the cast the ridge 

 corresponding to the skull groove for the superior sagittal sinus 

 is well marked throughout its length. Caudally this ridge bifur- 

 cates to the right and left, the former being slightly the larger, 

 and is lost in the wide tentorial groove. Before bifurcation the 

 sagittal ridge is joined obliquely on the left side and almost at 

 right angles on the right side by smaller tributary ridges. 



The cerebral fissural pattern on both hemispheres corresponds 

 in all essentials to that obtaining on the left in Specimen I. On 

 the right side of Specimen III there is, however, an additional 

 small compensatory sulcus caudal to the ramus descendens supra- 

 sylvii. Further, on the left side of this specimen, expansion of 

 the prominent gyrus lying between the suprasylvian and lateral 

 sulci, has been accompanied by a slight secondary longitudinal 

 folding with the formation of a short secondary sulcus. On the 

 caudo-lateral surface of the pyriform lobes on both sides, the 

 ridge corresponding to the infero-lateral venous sinus is well 

 marked. 



