certain Afferent and Efferent Tracts in the Medulla Oblongata. 75- 



In view of certain recent experimental observations responsible for 

 calling into question the existence of a direct anterior pyramidal 

 tract, evidence is adduced in support of the existence of this struc- 

 ture ; and the various direct efferent tracts met with in the spinal 

 cord are fully discussed. 



Among the conclusions based on the results of this experimental 

 inquiry, the following are to be found : — 



1. The descending antero- lateral tract, which degenerates in the 

 spinal cord after a lesion of the lateral region of the medulla, is prob- 

 ably the same as that met with after injury to Deiters' nucleus, and 

 is probably identical with that described by Marchi as degenerating 

 after lesions of the cerebellum, Motfc after injury to ground fibres and 

 some of the cranial nuclei, and Biedl after section of the restiform 

 body, its real source of origin being Deiters' nucleus, as contended by 

 Ferrier and Turner. 



2. The degenerated fibres which reach the anterior columns of the 

 upper part of the spinal cord through the posterior longitudinal 

 bundles, after a lesion of Deiters' nucleus, are quite distinct from the 

 above tract, and probably belong to some system of internuncial fibres 

 similar to those traced by Boyce to the anterior columns of the 

 spinal cord, by way of the posterior longitudinal bundles, after 

 hemisection of the mesencephalon. 



3. The direct descending tract of degenerated fibres met with in 

 the spinal cord in close relationship to the fibres of the crossed pyra- 

 midal tract, after a lesion of the lateral region of the medulla, is 

 probably identical with a similar tract described by Boyce after hemi- 

 section of the mesencephalon, and by Biedl after section of the resti- 

 form body and ascending root of the fifth nerve ; the proximity of 

 Boyce's columnar tract to the latter structure accounting for its 

 probable inclusion in Biedl's lesion. 



4. Fibres derived from the restiform body proper, and degenerating 

 caudalwards after section of this structure, do not form an efferent 

 tract in the spinal cord. 



5. There is no evidence that the " direct sensory cerebellar tract " 

 of Edinger is composed of afferent fibres, but, on the contrary, it 

 appears to be an efferent tract from the nucleus globosus to the 

 nucleus of Deiters, as suggested by Ferrier and Turner. 



6. One of the afferent tracts met with after a lesion of the lateral 

 region of the medulla corresponds so closely in position and distribu- 

 tion with the afferent antero-lateral tract of Gowers that it is highly 

 probable that they are identical, and accordingly that the observa- 

 tions of Mott and of Auerbach are correct in this connexion. 



7. Another efferent tract which degenerates after the lesion of the 

 lateral region of the medulla, and which is related to the fillet in. its 

 course to the region of the quadrigeminal bodies, is probably the 



