MYELINATED FIBERS—-PERONEAL NERVE OF RAT 413 
their peroneal nerves. In a group of seven operated stock albino 
rats of an average age of 161 days, referred to in the paper cited, 
the average number of peroneal fibers in the control nerves was 
2025. 
It is thus apparent that the normal animal, even at a slightly 
earlier age, has more fibers in its peroneal nerves than-were found 
in the intact (peroneal) nerves of operated animals. 
The average sectional area of 10 largest peroneal fibers from 
normal inbred albino rats of 153 days average age is 108.6 
square micra (taken from the original records and not shown in 
Table 4). In the previous study (Greenman, 713) the average 
sectional area of 10 largest peroneal fibers from the intact side 
of operated animals, of 189 days average age, was shown to be 
65.7 square micra. Thus it is seen that the normal animal even 
at a younger age has peroneal fibers of greater sectional area 
than those found in intact nerves of operated animals. 
' The present data support therefore the previous conclusion 
that in the operated rats the size of the fibers in the intact nerve 
was reduced. 
NUMBER OF PERONEAL FIBERS; SIZE OF LARGEST PERONEAL 
FIBERS IN A NORMAL ANIMAL 
The next step was to examine the largest fibers of both right 
and left peroneal nerves in a series of normal inbred animals 
and to determine whether symmetry of the right and left sides 
exists as regards the size of the largest fibers. 
Table 6 presents the data bearing upon this point. Here are 
given the measurements and counts of the fibers in the right 
and left peroneal nerves of 15 animals of same sex and strain and 
of about the same age. 
Here again it will be noted that the average number of fibers 
on the right side is practically identical with the average number 
on the left side—2038 on the iight side and 2032 on the left side. 
