1894.] On some of the Decussating Tracts of the Brain, fyc. 305 



statement that degenerated fibres from this source pass to the cranial 

 nerve roots through the posterior longitudinal bundles, and to the 

 antero-lateral columns of the cord by way of the fillet. 



With regard to the well-marked antero-lateral tract, which Marchi 

 describes as degenerating throughout the whole length of the spinal 

 cord, it is held, in conjunction with Ferrier and Turner, that no such 

 tract degenerates after lesions limited to the cerebellum. And in sup- 

 port of this negative view being probably the correct one, is adduced 

 the fact that Ferrier and Turner found a similar tract after injury to 

 Deiter's nucleus, as did Mott also, after injury to the posterior 

 column nuclei. 



XXI. " A Contribution to the Study of (i) some of the Decussa- 

 ting Tracts of the Mid- and Inter-brain, and (ii) of the 

 Pyramidal System in the Mesencephalon and Bulb." By 

 HUBERT BOYCE, M.B., Assistant Professor of Pathology in 

 University College, London. Communicated by Professor 

 VICTOR HORSLEY, F.R.S. Received June 9, 1894. 



(Prom the Pathological Laboratory of University College, London.) 

 (Abstract.) 



The present paper is supplementary to a paper communicated to 

 the Royal Society, February, 1894, entitled a " Contribution to the 

 Study of the Descending Degenerations in the Brain and Spinal 

 Cord." It is based upon a study of the changes found in the brains 

 and spinal cords of the animals (cats) used for that research. 



1. It is found that hemisections of the mesencephalon through the 

 superior quadrigeminal region is followed by degeneration of 

 Meynert's commissure and Forel' s decussation, situated in front of the 

 third ventricle and behind the optic chiasma. 



The degenerate fibres which go to form the decussation of Forel are 

 large medullated fibres which ascend from the seat of injury in the 

 tegmental region, proceed forwards and anteriorly, and then curve 

 round in front of the third ventricle, between the latter and Mey- 

 nert's commissure. They then pass backwards, between the optic 

 tract and the internal capsule (pes pedunculi), and appear to end in 

 the lateral thalamic region. This description agrees with that given 

 by Darkschewitch and Pribytkow, who, however, state that the 

 fibres terminate in the lenticular nucleus; by the Marchi method, 

 on the other hand, the Author has traced the fibres past this nucleus, 

 and across the internal capsule into the thalamus. 



The fibres appear to be part of the fibres constituting the " foun- 

 tain (ventral) decussation of Forel." 



VOL. LVf. X 



