492 M. J. GREENMAN 



Passing next to the distal side of the lesion and dividing the 

 five available records into two groups, one group including the 

 enumerations between the lesion and 1.5 mm. distal to the lesion, 

 the other group including those between 1.5 mm. and 3.1 mm. 

 distal to the lesion and omitting all those in which sections were 

 lost, as well as the records of no. 100, we obtain the following: 



1 The control averages for these groups are 2069 and 2067 respectively. 



Table 6 shows that there is an 80 per cent increase in the 

 number of fibers over the control average in the first group 

 located between and 1.5 mm. distal to the lesion and a 64 

 per cent increase over the control average in the second group 

 located between 1.5 and 3.1 mm. distal from the lesion. 



From these enumerations it is evident that, following the com- 

 plete degeneration which extends from 2 to 3.2 mm. proximally 

 from the lesion there occurs in the course of regeneration a 

 branching growth of the axis cylinders which appears to take 

 place at considerable distance above the point at which complete 

 degeneration terminates. This branching results in an increase 

 of about 80 per cent in the number of medullated fibers as the 

 region of the lesion is approached; this increase diminishes as 

 the distance distal to the lesion increases. This decrease in ex- 

 cess fibers distal to the lesion is probably due to the failure of 

 a portion of the fibers to continue their development for any 

 considerable distance beyond the lesion. 



In specimen no. 100, age 61 days at the time of operation, it 

 will be noted (see table 3) that when killed, 105 days after oper- 

 ation, the animal had increased in weight only 1.5 grams. This 

 failure to grow is also accompanied by a reduction in the number 

 of regenerated fibers most marked on the distal side of the lesion 

 where at a distance of 3.4 mm. from the lesion only 18 medul- 



