Secondary Degenerutioii following Unila,ter!i,l Lesions etc. 325 



into the formatio reticularis of tlie- opposite side and still tewei' into 

 tliat of the same side. In the lower levels of the decussation a few 

 small bundles of degenerated fibres (homolateral) passed to the cros- 

 sed pyramidal tract of the same (left) side, and in the spinal cord a 

 few fibres forming a direct lateral pyramidal tract were seen which 

 were traced as far as the 4*^ sacral segment. No direct anterior 

 pyramidal tract was found in any of the animals examined. 



With regard to the connection between the grey matter of the 

 optic thalamus and the pyramidal tract Monakow [11] as early as 

 1884, employing the method of von Gudden [12], removed the motor 

 area on one side in rabbits and cats, and as a result found, amongst 

 other things, atrophy of the grey matter of the optic thalamus of the 

 same side. Amongst recent observers Boy ce [13] in the cat, in 1894 

 and Melius [14] in the monkey, in the same year, both using the 

 method of Marchi, were able to trace fibres from the pyramidal tract 

 into the optic thalamus of the same side. 



Many investigators have found either atrophy of, or fine (termi- 

 nal) degeneration in the substantia nigra in relation to the degenerated 

 crusta according to the method employed. Monakow [11] in 1884 in 

 rabbits and cats, Sherrington [-Z5] in 1890 in monkeys, Langley and 

 Grünbaum [16] in the same year in a dog. Melius [14] in 1894 in 

 monkeys, and Dejerine and Long [17] in 1898 in the human subject, 

 have recorded their observations on this point. 



Fibres passing from the crusta to the anterior corpora quadri- 

 gemina have been previously observed by only two workers so far as 

 I know, viz: — Muratoff [18] in 1893 and Boyce [13] in the follow- 

 ing year. Boyce describes them in two cats as isolated fibres coming 

 off from the outer extremity of the degenerated crusta and curving 

 round to the quadrigeminal region. Muratoff figures them as passing 

 towards the lateral border of the central grey matter. I have not 

 found these fibres in the dog or in either of the two monkeys which 

 I have examined, but they were present in 14 out of the 16 cats ex- 

 perimented upon, and in several cases they were ver}^ numerous. 

 They do not come off from the outer extremity alone, as stated by 

 Boyce and Muratoff, but from the whole posterior aspect of the de- 



