Secondary Degenenitiou following Unilateral licsions etc. 3] 7 



wards tlie base of tlie posterior horn and a varyin;^ amount of fine 

 deg-eneration is present in the grey matter of this region (fig-. 4. pi. XVII). 

 A few homolateral or uncrossed degenerated fibres, varying in number 

 in the different animals, occupy a corresponding- position in the lateral 

 column on the side of the lesion. In the dorsal, lumbar and sacral 

 i-egions (figs. 5 and 6. pi. XVII), (beyond the 4*^^ sacral segment no section 

 was examined) fibres representing both direct and crossed lateral pyrami- 

 dal tracts are present in gradually diminishing numbers. In most of 

 the cases the direct lateral pyramidal tract (homolateral fibres) is still 

 represented at the level of the 4*^ sacral segment. In sections through 

 the lumbar enlargement a few fibres can be made out on the right 

 side passing from the degenerated crossed pyramidal tract into the 

 grey matter at the base of the posterior horn. In no case was there 

 any evidence of a direct (anterior) pyi-amidal tract. 



I had intended to count the degenerated fibres at different levels 

 in order to find out in what regions throughout tlie brain and spinal 

 cord they disappear in greatest number, but on making the attempt 

 I found that the time and means at my disposal would not admit of 

 this being done with any degree of accuracy. 



Dog. 



Lesion. A description of the lesion and the symptoms following, 

 it in the dog examined by me, are given by Professor Schäfer in the 

 Proceedings of the Physiological Society, Jan. 26*'^ 1901. It is as 

 follows: — "In the dog experimented on, a cut 5 — 7 mm deep was made 

 well around the sigmoid gyrus. The result of this was to produce 

 paralysis for voluntary motion (inability to hold a bone, awkwardness 

 in walking) and blunted sensibility on the opposite side, and also at 

 first homonymous hemianopsia, which however had disappeared by the 

 5*^ day. The animal was killed one month after the operation; the 

 circumsected area gave no result on stimulation." 



Secondary Degeneration. Coronal sections through the posterior 

 part of the optic thalamus and internal capsule show the bundles of 

 the internal capsule on the left side markedly degenerated throughout 

 its middle three-fifths, and from these bundles fibres pass into the grey 



