XXX Journal of Comparative Neurology. 



It would be difficult to give even an approximately complete ac- 

 count of the observations made by Ballance and Stewart, on the de- 

 generative and regenerative changes observed in severed peripheral 

 nerves, within the limits set for a review, since the greater portion of 

 their monograph consists of a description of the experiments made and 

 of a record of detailed observations made on sections obtained from tis- 

 sues derived from such experiments. Consideration will, therefore, be 

 given mainly to the deductions made by them, based on a study of their 

 preparations and, in doing so, more particular attention will be paid to 

 their interpretation of the appearances presented by sections showing 

 the regenerative processes in severed peripheral nerves, as their obser- 

 vations can not be said to contribute materially to current views held 

 concerning the degenerative changes occurring in injured peripheral 

 nerves. 



In 36 experiments, the severed nerve was removed, sectioned and 

 stained after Weigert's differential myehn staining method. In the 

 end of the nerve proximal to the place of section, new sheaths (regen- 

 erating nerve fibers) were found as early as the end of the second 

 week. Near the place of division, the new sheaths are said to appear 

 in small isolated groups, "whose general direction is sinuously longi- 

 tudinal." "At a higher level, adjacent islands of the same longitudinal 

 series have become a continuous tubular plexus within the neurilemma, 

 and higher still the plexus is continuous with the end of the normal 

 sheaths." Particular stress is laid on the fact that in the neighborhood 

 of the wound, the new sheaths appear in the form of isolated groups. 

 The new sheaths are said to be in close opposition to the cells of the 

 neurilemma, which do not share in the degenerative process. Distal 

 to the place of section, new sheaths are visible at the end of the third 

 week and at the end of the following week, they are numerous through- 

 out the entire nerve. In the connective tissue between the distal and 

 proximal segments, the new sheaths are scanty at the end of the fourth 

 week. 



Nerve tissues taken from experiments numbering from 38 to 41 

 were treated after Cox's modification of the Golgi method. In the 

 preparations showing regeneration, Ballance and Siewart observed 

 peculiar cells, impregnated by means of the Cox method, to which they 

 give the name "spider cells." These cells are not especially described, 

 but are abundantly figured on Plates 5 to 12. They appear to consist 

 of a cell body of round or oval shape (somewhat irregular), with numer- 

 ous processes, which extend generally from opposite poles. The term 

 "spider cell" must be regarded as unfortunate, unless the cells here un- 



