164 PROFESSOR W. H. THOMPSON. 



found that the portion of the pyramidal tract destined for the 

 lateral column when it reaches the medulla, and rises dorsally 

 prior to decussation, divides into two portions ; a larger which 

 crosses over into the lateral column of the opposite half of the 

 spinal cord, and a smaller which is continued on into the 

 lateral column of its own side. It is, I should venture 

 to say, quite likely that the direct pyramidal bundle also ends 

 bilaterally. Further, the manner in which the optic tract 

 terminates in both retina? is not without interest to call to 

 mind in this connection. 



Since I have no doubt that the same rule applies to other 

 areas of cortex than those of the temporal lobe, one might 

 therefore formulate a lain of bilateral connection hettoeen a 

 given portion of cortex, and all the more distantly situated masses 

 of grey matter with which it is associated. 



Before concluding, I have to thank Dr Cecil Shaw for kindly 

 making the photographs for me. 



Summary of Eesults. 



I. Degeneration was detected in the following sets of fihrcs : — 

 (1) In short association, fibres passing to neighbouring parts of 

 the cortex. (2) In longer association bundles, viz., inferior 

 longitudinal fasciculus, and parieto-temporal fasciculus, leading 

 to occipital and parietal lobes respectively. (3) In the tapetum, 

 some of these fibres passed back into the occipital lobe on the 

 side of the lesion ; others crossed over in the corpus callosum to 

 the tapetum of the opposite side, by which they were likewise 

 conveyed backwards and downwards into the occipital lobe. 

 (4) In the external capsule, some being distributed to the anterior 

 and lower part of the cerebrum, others crossing over in the 

 anterior commissure to the opposite temporal lobe. (5) In the 

 corpus callosum, one set leading to the opposite temporal cortex, 

 another descending in internal capsule. (6) In the internal 

 capsule, the main bundle of descending degeneration occupying 

 the retro-lenticular segment of the posterior limb on the side of the 

 lesion. Its fibres were distributed in the first instance to the back 

 part of the optic thalamus, the corpus geniculatum internum, 

 and to both corpora quadrigemina. An additional set descended 



