162 PKOFESSOR \V. H. THOMPSON. 



The view that the corpus callosum contains other than direct 

 commissural fibres, which was first set forth by Ramilton,'^ received 

 much opposition. It has, however, been confirmed by the experi- 

 ments of Bianchi and cVAhundo^- in connection with cortical local- 

 isation ; by those of Shaio and myself on the occipital lobe ; and 

 also by those of Ferrier and Turner^ on cortical afferent and 

 efferent tracts. Finally, Dotto and Fusateri * also support this 

 view. These workers divided the corpus callosum at its hinder 

 part in cats, and as a result were able to trace degenerated fibres 

 downwards through the capsules into the mid-brain, and thence on 

 into the medulla. Some were even followed into the spinal cord. 

 The liability to injury of adjacent parts of the motor cortex, 

 which such experiments involve, has been pointed out by Dejcrinc,^ 

 and he attributes the degenerations which are traceable down- 

 wards to such cause. 



I can confirm the statements of Dejerinc with regard to the 



liability to injury, but I would point out that such possibility 



did not arise in the present series of experiments, nor did it in 



those of Ferrier and Turner. 



These descending callosal fibres can hardly be regarded as 



" projection fibres " in the ordinary acceptance of this term. 



They are more to be considered as contra-lateral association 



fibres, a view which would equally apply to all of the fibres 



composing the corpus callosum. 



Mid-hrain. — Besides the degenerated fibres already mentioned 

 as being found in the mid-brain, others also occurred in both 

 fillets. These were detected in the highest sections made 

 through the crura, and were even more numerous here than in 

 sections lower down. They could not, therefore, have wandered 

 in from other crural tracts, possessing such fibres, and must 

 consequently have descended from the internal capsules. 



' Hamilton, D. J., op. cit. 



^ Bianchi, L., e d'Abundo, G., " La degeneraz. speriment. nel cervello e nel' 

 midollo spinale, etc.," La Psychlatria, 1886; also, "Die in das Gehirn u. 

 Rlickeuniark heiabsteig. Experini. Degener. als Beitrag z. Lehre v. ceveb. 

 Lokalisation," Neurol. Centralbl. v. 17, 1886. 



3 Ferrier and Turner, op. cit. 



« Dotto e Pusateri, ' ' Sul de corso delle fibre del Corp. Callos. e del Psalterium," 

 Riv. dipatol. tiervement, pp. 69-70. 



5 Dejerine, J., Anatomie dcs Centres Nervcux, Paris, 1895, p. 765. 



