198 Proceedings of the Royal Irish Academy. 



Stjmmaky of Resttlts. 



I. Degeneration was detected in the folloioing sets of fibres : — (1) In 

 short association, fibres passing to neighboming 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 into the outer fifth of 

 the pes pedunculi, reaching as low as the pons, ^^''here it terminated 

 bilaterally. Other scattered degenerations were seen in the greater 

 part of the posterior limbs of both capsules. These were traced into 

 corresponding parts of the peduncles, and on into the pons. Fibres 

 from this source were contributed to the optic thalami, the substantia 

 nigra, and mesencephalic grey matter. (7) Lastly, in both fillets, 

 crossing from the internal capsules, and gradually disappearing in the 

 mid-brain. 



II. A laiv of hilateral association seems to prevail in the connexions 

 established between a given area of cortex and other distantly situated 

 masses of grey matter, whether subserving ' motor ' or ' sensory ' func- 

 tions. 



I^.B. — The expenses of this research have been defrayed by grants 

 fi'om the Royal Society and Royal Irish Academy. 



