304 Experimental Lesions of the Cerebellum. [June 21, 



of the lesion decussate in the posterior quadrigeminal region, and 

 pass to the opposite red nucleus and optic thalamus. None could be 

 traced beyond this point. Those in the opposite superior peduncle 

 represent fibres which degenerate in the cerebellum, passing from 

 the seat of lesion across to the intact half of the organ, and leaving it 

 by this peduncle. These degenerated fibres occupy a special position 

 in the peduncle, a part of it which is comparatively free from 

 degenerated fibres on the side of the lesion, and a part occupied by 

 degenerated fibres on both sides, when the cerebellum is divided into 

 two lateral halves by a mesial incision. These facts are held to con- 

 trovert Marchi's statement, that none of the peduncles contain 

 commissural fibres. 



The degenerated fibres in the middle peduncle, on the side of the 

 lesion, pass chiefly to the grey matter of the opposite side of the pons. 

 Some degenerated fibres from this source pass between the pyramidal 

 bundles, but there is no evidence to support Marchi's observation, 

 that degenerated fibres also pass from this peduncle in the fillet and 

 posterior longitudinal bundle to the corpora quadrigemina and peri- 

 phery of the antero-lateral region of the spinal cord, and that some 

 pass to the corpus striatum by way of the pyramidal tract. 



Of the fibres which degenerate in the inferior peduncle, the 

 majority occupy the lateral region of the medulla, becoming more and 

 more scattered as they pass down. These can no longer be said to form 

 a tract below the level of the superior pyramidal decussation ; but a 

 few scattered degenerated fibres occupy the antero-lateral region of 

 the cervical cord, beyond which none can be traced. Degenerated 

 fibres pass to both inferior olives from this peduncle ; but no well- 

 marked tract to the opposite inferior olive, as described by Ferrier 

 and Turner, was found. In accordance with these observers, how- 

 ever, no corroboration of Marchi's results was found, in so far as he 

 states that degenerated fibres pass from this peduncle to the ascending 

 root of the fifth, the roots of the cranial nerves through the posterior 

 longitudinal bundles, and the spinal nerves by the descending antero- 

 lateral tract. 



In confirmation of Marchi, and contrary to the observations of 

 Ferrier and Turner, degenerated fibres were found in all the 

 peduncles of the cerebellum, after extirpation of its middle lobe. 

 Those in the superior peduncle occupy all parts of it, as seen on 

 transverse section, they decussate in the region of the posterior 

 corpora quadrigemina, and terminate in the opposite red nucleus, 

 beyond which point no degenerated fibres could be traced. 



The degenerated fibres in the middle peduncle behave much as do 

 those which result from ablation of one lateral lobe of the cerebellum, 

 and the same may be said with regard to the degenerated fibres in 

 the inferior peduncle. No evidence was found to support Marchi's 



