484 M. J. GREENMAN 



Passing to the histological changes following the operation, 

 we find on the fourth day after operation that all the medullated 

 fibers distal to the lesion show appearances characteristic of 

 degeneration. Crushing, therefore, interrupts the fibers com- 

 pletely. This degeneration extends from the point of crushing 

 distally as far as observations have been made — that is, from 

 5 to 8 mm. — and it was assumed that the degeneration had- 

 extended to the termination of each fiber. In the other direc- 

 tion, degeneration extended from the point of crushing proxi- 

 mally from 2 to 3 mm.- — according to actual measurements, from 

 2 to 3.2 mm. Above this point the structure of the great ma- 

 jority of the fibers appeared to be normal with here and there one 

 modified in a way to suggest degenerative changes even as much 

 as 8 mm. proximal from the point of lesion. Similar changes 

 in structure have been figured by Boll (76) and described as 

 due to histological methods. I am inclined to think that the 

 changes here observed are preparatory to the regenerative proc- 

 ess which is about to begin and which I have found by numeri- 

 cal determinations to begin as much as 7 mm. proximal to the 

 lesion. Ranson ('12) finds in dogs that non-medullated fibers 

 degenerate more than 10 mm. up the proximal stump where re- 

 generation begins. 



Perroncito ('06) has shown that a sectioned axone begins to 

 regenerate within three hours after cutting. In the present ex- 

 periments no animals were killed earlier than three days after 

 operation and from that period up to 105 days. No effort has 

 been made here to trace the earliest development of the new 

 fibers. 



To determine the time when degeneration in the rat was 

 complete, six animals were killed as follows: One 3 days after 

 operation, two 4 days after operation and three 6 days after 

 operation. Two of these animals were 89 days and four were 90 

 days of age at the time of operation. Series 5. 



The three-day and the four-day animals showed complete de- 

 generation of all fibers and the clinical signs indicated complete 

 loss of control of muscles supplied by the peroneal. The six- 

 day animals showed complete degeneration, but the clinical signs 



