144 SUTHERLAND SIMPSON 



behind the crusta; these do not appear to be running dorsal- 

 ward into the tegmentum, as they are frequently observed to 

 do in the cat and other animals at this level. Their course is 

 cephalo-caudal, and they probably represent straggling bundles 

 detached from the main mass of the tract. 



Fig. 1 Brain of red squirrel, dorsal view, showing position of lesion in left 

 cerebral hemisphere. Magnified \. 



Transverse section near junction of mid-brain and pons through 

 posterior corpora quadrigemina (fig. 3). The tract is now com- 

 pacted into a single oval-shaped bundle lying just behind the 

 superficial transverse fibers of the pons. Its long diameter ex- 

 tends from before backward and outward. This area contains a 

 large number of degenerated fibers scattered uniformly over its 

 entire surface; none can be seen leaving the bundle on any of 

 its aspects. 



Transverse section through middle of pons {fig. 4). The out- 

 line of the tract is still more or less oval with a slight projection 

 at the inner angle. The bundle is single and compact, not broken 

 up by the transverse pontine fibers as is the case in the cat, dog 

 and monkey, for example; the black dots are very numerous and 

 are scattered over the whole area. Fine degeneration is very 

 abundant amongst the cells of the nuclei pontis on the mesial, 

 ventral and lateral aspects of the tract; it fades away towards 

 the middle line and does not extend beyond the raphe. No 

 degenerated fibers are to be seen in the mesial fillet lying behind 

 and internal to the p3Tamid tract. 



