382 Journal of Comparative Neurology and Psychology. 



The second group of observations opposed to the state- 

 ment formulated by Waller has been derived from experiments 

 intended to locate the nuclei of origin of the motor nerves. 

 The tearing out of motor nerves is followed by atrophy or dis- 

 appearance of their intramedullary roots and nuclei of origin. 

 (Literature summarized by Fokel, '87.) A true degeneration 

 of the central ends of these fibers can be demonstrated by the 

 method of Marchi (Bregmann, '92, Dakksciiewitscii, '92). 



In the central nervous system a retrograde or cellulipetal 

 degeneration has been observed in seven localities. A descend- 

 ing degeneration has been seen in the optic radiation after ex- 

 cision of its terminal ramifications in the occipital cortex (von 

 MoNAKOW, '84, MoELi, '93) and in the medial lemniscus after 

 injury to the central gyri (von Monakow, '85, Greiwe, '94, 

 Klippel and Durante, '95). The retrograde degeneration in 

 these tracts differs in some cases histologically from Walle- 

 rian degeneration, the axis cylinder remaining intact while the 

 myelin sheath disappears, although in most cases it resembles 

 true secondary degeneration very closely. Often this cellulipe- 

 tal degeneration is very extensive, involving the majority of the 

 fibers of the trac t. For these reasons, the downward degen- 

 eration in the optic radiation and in the lemniscus cannot be ad- 

 duced as evidence for a double pathway. Similar observations 

 have been made on the pyramidal tract, which in certain cases 

 has degenerated cephalad after a transverse lesion of the spinal 

 cord (WiLLAMSON, '93, Raymond, '94). 



Van Gehuchten has shown that degeneration of the prox- 

 imal part of injured nerve fibers may occur in the middle cere- 

 bellar peduncle, in the fibers passing from the nucleus ruber to 

 the lateral fasciculus of the spinal cord, in the fibers passing 

 from the nucleus of Deiter.s to the anterior fasciculus of the 

 cord, and in those from the cells of the formatio reticularis of 

 the pons and medulla to the anterolateral fasciculus of the cord. 

 That retrograde degeneration occurs in these tracts and not 

 merely the Wallerian degeneration of a second pathway, is 

 supported by the facts that the changes in question do not ap- 



