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Proceedings of the Royal Irish Academy. 



mesencephalon. They were no doubt continued fi'om the capsular set of 

 fibres, and would thus supply the cross link for a bilateral termination 

 of the sets of fibres with which we are now dealing. That such bilateral 

 method is the general plan of connexion between a given portion of 

 the cortex and other masses of grey matter I have little doubt. 



Lastly, a very definite fasciculus continued downwards in the 

 internal capsule, traversing the sub-thalamic segment of this tract (see 

 d. 1. fig. 7), and from thence passed into the outer part of the pes 

 pedunculi. In the sub-thalamic region the degenerated fibres were 

 found to occupy the posterior part, distributed amongst certain of 

 the bundles of fibres into which the system is here subdivided (see 



a 4 



d.5. 



/t6. 



Fig. 8.— Vertical section througli same brain as figs. 5, 6, and 7, but 

 posterior to fig. 7 ; showing degenerations in : — 



d. 1. posterior part of internal capsule (subthalamic region). 



d. 2. inferior longitudinal fasciculus. 



d. 3. extending from tapetum into occipital lobe. 



d. U' tapetum of opposite side. 



d. 5. posterior commissure. 



d. 6. and 7. scattered through middle parts of internal capsules. 



d. 8. traversing optic thalamus to reach corpora quadi-igemina. 



d. 1. fig. 8), but leaving others wholly free. These latter, which 

 no doubt for the most part represent the projection system of 

 the occipital lobe, were not always the most posteriorly situated. 

 Quite a common arrangement was to find a small degenerated bundle 



