208 Dr. E. L. Melhis. Experimental Degenerations [June 13, 



intra-parietal sulcus and the fissure of Rolando, and a little above the 

 inferior genii of the fissure of Rolando (Beevor and Horsley). In 

 these cases the majority of the degenerated association fibres pass to 

 the ascending frontal and ascending parietal convolutions, rather 

 more to the latter than to the former. In these lesions of the 

 thumb centre degenerate fibres were distributed to these two convolu- 

 tions from the border of the longitudinal fissure nearly to the fissure 

 of Sylvius, the fibres passing upward from the lesion being coarse, 

 while those passing downward were fine. Fine degeneration was 

 traced into the posterior portion of the middle and inferior frontal 

 convolutions, and in one case to the supra marginal and angular gyri. 

 In two cases it was also found passing to the upper or posterior 

 portion of the superior temporal convolution. In various instances 

 a few degenerate fibres passed to the precuneus and lobus quadratus 

 and paracentralis and to the gyrus fornicatus. 



There is considerable variation in the size of the fibres crossing 

 in the corpus callosum after lesion of the thumb centre. With 

 slight variations it was situated in the middle third. The distribu- 

 tion of the degenerate fibres to the convolutions of the right 

 hemisphere corresponds very closely to that in the left, though 

 less in amount and slightly less in area. The same arrangement 

 of the coarse and fine fibres observed on the left side prevails on 

 the right coarse above the lesion, fine below. The degeneration 

 passing from the lesion downward through the centrum semiovale is- 

 both coarse and fine. These fibres are more scattered and the area 

 of degeneration is greater than that in lesions of the hallux centre, 

 both laterally and antero-posteriorly. In one case only was there 

 any apparent separation of the coarse and fine fibres in the centrum 

 semiovale, and there the coarser fibres were anterior to the fine. The 

 same arrangement prevails in the internal capsule, the coarser fibres 

 representing the pyramidal fibres being found (in the lower levels) 

 in the middle third of the posterior limb, while the fine fibres, mostly 

 representing the corona radiata thalami, are largely situated in the 

 posterior third of the posterior limb. Between the upper and lower 

 levels of the capsule there is a movement of the degeneration for- 

 ward, and in the lower levels most of the fine degeneration has 

 already passed into the thalamus. In one case a little fine degenera- 

 tion v/as found in the right internal capsule occupying a position 

 corresponding to that of the fine degeneration in the left capsule. 

 This all passed into the right thalamus. In another case both coarse- 

 and fine degenerate fibres were found in the right capsule occupying 

 the same position and pursuing the same course as the corresponding 

 fibres on the left side. These fibres come from the area of degenera- 

 tion in the right centrum semiovale, into which the fibres crossing in 

 the corpus callosum could be traced, but no continuous fibres could 



