1895.] following Unilateral Lesions of the Cortex Cerebri. 213 



exactly the same appearances were found in the brains of control 

 animals in which there was no lesion. 



In the general summary attention is called to the fact that the dis- 

 tribution of the degenerate association fibres in the thumb lesions corre- 

 sponded with the measurements made by Bevan Lewis of the corpuscles 

 of the fourth layer of the cortex in this region, i.e., that coarse fibres 

 were distributed to the upper part of the motor area and fine fibres 

 to the lower part. In four of the experiments (one thumb and three 

 facial) neither pyramidal fibres nor fibres connecting the nuclei of the 

 cranial nerves directly with the cortex were found to have degene- 

 rated. Yet in each of these cases the characteristic movement was 

 obtained from stimulation of the area removed quite as readily as in 

 any other case. The degenerate fibres passing through the internal 

 capsule in these cases apparently belong to two distinct systems, 

 which are also more or less represented in the other experiments. 

 One of these, composed almost entirely of fine fibres, passes from the 

 posterior limb of the internal capsule into the outer surface of the 

 optic thalamus, and represents the corona radiata thalami. These 

 fibres are to some extent mixed with the pyramidal fibres in the 

 posterior limb of the internal capsule, but are mostly situated in the 

 posterior third, and, as they pass from there into the thalamus, make 

 room for the entrance of the sensory (non-excitable) tract. The 

 other of the two systems referred to, largely composed of coarser 

 fibres, passes through the internal capsule into the crns, and appa- 

 rently ends in the substantia nigra. These fibres are of much the 

 same calibre, and apparently occupy the same position in the internal 

 capsule and crus as the true pyramidal fibres. Both these tracts 

 appear to arise in all portions of the motor cortex coming within the 

 range of these experiments. All the degenerated pyramidal fibres 

 from the hallux and thumb lesions were found to enter the capsule at 

 or near the posterior extremity, while the corresponding fibres from 

 the facial lesions entered the capsule at or near the anterior 

 extremity, and the former were displaced forward and the latter 

 backward until in the lower levels of the capsule they all found a 

 place in the middle third of the posterior limb. It is also shown that 

 a line can be drawn from the fissure of Sylvius upward, so dividing 

 the motor area into two parts, that all the facial lesions from which 

 fibres enter the anterior portion of the capsule would be in the 

 anterior division, and all the hallux and thumb lesions from which 

 fibres enter the posterior portion of the capsule would be in the 

 posterior division. In the movement of the facial fibres backward 

 between the upper and lower levels of the capsule they would 

 necessarily, at some level, envelop the genu, which would account 

 for the fact that they have always been described as occupying that 

 position. The location of these degenerations in the internal capsule 



