MYELINATED FIBERS—PERONEAL NERVE OF RAT 411 
The variability in number is shown by the following deter- 
minations. 
In making these determinations the formulas given by Daven- 
port (’99) have been used for the standard deviation, c, the coeffi- 
cient of variability, C, and the probable errors of these, as well 
as of the mean, M. 
Number of fibers in right peroneal nerve—average of 12 cases. Average age 
153 days. 
M (mean) 2071 Nie — es 
o 96 ee ee 
C 4.6 C.= + 0.60 
Number of fibers in left peroneal nerve—average of 12 cases. Average age 
153 days. 
M (mean) 2069 Nie — aly, 
o 87 Oo. = + 11.9 
G 4.2 . Ce = + 0.54 
In examining the sectional area of fibers we note that in 
8 of the 12 cases the fibers of the right or stimulated nerve are 
less in sectional area than those of the left nerve. In one case 
(No. 363) the difference is large. 
Taking the average sectional area of the stimulated fibers 
we find it to be 93.7 square micra, while the average of the left 
fibers is 98.4 square micra. The difference here shown between 
the averages is 4.7 square micra or approximately 5 per cent of 
the smaller number. 
An examination of these measurements by the usual statis- 
tical methods gives the following results, table 5. 
TABLE 5 
Right peroneal Left peroneal 
Stimulated fibers Control fibers 
M (mean) 93.7 sq. micra M, = += 2.3 M (mean) 98.4 sq. micra M, = + 1.1 
. 11.8 G= = 1.66 5.9 oc = +08 
G 12.6 Ca LC 6.0 Caso 
The difference obtained between the stimulated and the con- 
trol fibers is 4.7 square micra. The probable error of this determi- 
Mation 1602.5. 
