314 S. Simpson, 



In transverse sections of tlie mid-brain through the anterior cor- 

 pora qnadrig-emina the left crusta is found to be studded with de- 

 generated fibres over its whole area, with the exception of a thin 

 zone along its ventral border which is, in some cases, almost free 

 from degeneration. At this level also the lateral extremity of the 

 crusta is either free from or contains very few degenerated fibres. 

 Numerous degenerated fibres pass backwards from the crusta through 

 the substantia nigra, into and through the tegmentum towards the 

 anterior corpus quadrigeminum of the same side, and in many cases 

 they can be traced to the grey matter of that corpus in which they 

 appear to end; in one or two of the cases a few are seen to curve 

 round close to the posterior (superior) surface, and crossing in the 

 roof of the aqueduct, to become lost in the quadrigeminal body of the 

 opposite side see (fig. 1 pi. XVI). These fibres are present more or less 

 numerously in all the cats experimented upon with two exceptions. In 

 only one or two cases are any fibres seen to enter the grey matter 

 around the S3'lvian aqueduct, and these do not appear to end there 

 but to be continued through the lateral portion of it in their course 

 towards the anterior corpora quadrigemina. In most of the cases 

 throughout the whole of the mesencephalon there is a varying amount 

 of fine degeneration in the grey matter of the substantia nigra poster- 

 ior to the degenerated crusta. In sections of the posterior part of 

 the mesencephalon (through the posterior corpora quadrigemina) the 

 left crusta is degenerated throughout its whole extent, no antero- 

 lateral marginal zone being free as is the case at a higher level. In 

 one or two instances a few fibres pass backwards from the outer 

 extremity of the degenerated crusta into the tegmentum but they 

 can not be traced to any distance, — none can be traced to the 

 post, corp, quad. 



Transverse sections at different levels in the pons Varolii show 

 the pyramidal bundles on the left side to be tilled with (U^gcncralcd 

 fibres, — coarse, medium, and fine. In some of the cases a few scat- 

 tered tibi-es are seen in the hiteial i)()rtion of the mesial fillet, behind 

 the, (l('g(;nerated i)yi-amidal Inuidles. 'i'liciv is vciy abundant fine de- 

 generation scattered amongst the cells ot llic nuclei jtontls lateral, 



