196 Proceedings of the Roijal Irish Academy. 



Finally, Dotto and Pusateri'^ 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 Kability to injury of adjacent parts of the motor cortex, which 

 such experiments involve, has been pointed out by Bejerine,'^ and 

 he attributes the degenerations which are traceable downwards to such 

 cause. 



1 can confii'm the statements of Bejerine, with regard to the lia- 

 bility 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 descendiag callosal fibres can hardly be regarded as ' ' pro- 

 jecting 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 abeady mentioned as being found in 

 the mid-brain, others also occurred in both fillets. These were 

 detected in the highest sections made through the crui'a, 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. Further, from the fact that the numbers were about equal 

 on both sides, from the first, I take it that those of the contra-lateral 

 bundle must have crossed over in the corpus callosum. 



The existence of fibres directly connecting the cortex with the 

 mid-brain, through the medium of the internal capsule, has been 

 shown by numerous observers. It was first stated by V. Gudden,^ 

 and has since been confii-med by Flechdg,^ and V. Monakow.^ V. 



1 Dotto e Fusateri. " Sul de corso delle fibre del Corp. Callos e del Psalterium," 

 Eiv di patol. nerve e ment, p. 69-70. 



•Bejerine, J., Anatomie des centres nerveux : Paris, 1895, p. 765. 



^ V. Giiclden, " Gesammelte Abhandlungen." 



^ Flechsig, " Zur Anat. u. Entwick. Geschicht. d. Leitungs-B. i. Grossh. d. 

 Menschen," Arch. f. Anat. u. Physiol. Anat. Abth., 1881, 12-75. 



'" Monakow, "Experim. Beitrage z. Kenntn. d. Pyramiden u. Schleifenbahn" 

 Beferat. Neurol. Centr. 1883, s. 197-198; s\&o lUd. 1885, s. 265-268; also 

 Deutsche Med. Wochenschr. , xi., 5, s. 79. 



