240 JOURNAL OF CoMPARATIVE NEUROLOGY. 
TABLE XVIII. 
Number of fibers to the several segments of the right leg of Frog B IT. 
Estimated Observed 
(DONALDSON) (DuNnN) 
To thigh 3269 3508 
To shank 1796 2130 
To foot 2042 2497 
Thus in every case the numbers estimated by the formula 
are less than those observed by Dr. Dunn. But as Table XIV 
shows, Dr. Dunn’s count includes a large number of fibers 
which have split (see ‘‘splitting fibers” in tables), and which, 
therefore, are not taken into account by the formula, which 
applies to single pathways only. 
The next step, therefore, in the comparison is to bring the 
two series of numbers to the same standard. There are two 
ways of doing this, namely, either by removing the additional 
fibers due to splitting from the number observed by Dr. Dunn, 
or by adding the additional fibers to the number as determined 
by the formula. The latter method was followed; first, 
because it was desirable to consider the odserved number as the 
fixed standard, not to be altered in any way, and second, 
because it seems probable that the most direct utilization of 
this formula will be for determining the number of fibers which 
a direct count would show to be supplied to a given segment. 
Thus in the further work, the observed number is in each 
case taken as the standard, and the calculations are directed to 
determining the number which must be added to that estimated 
by the formula in order to make it comparable with the stand- 
ard. To illustrate the stéps taken for this purpose, we shall do 
best to examine the innervation of the thigh in the case chosen, 
namely, the right leg of Frog B H. My estimation gives for 
the thigh 3269 fibers and Dr. Dunn’s observation 3508. 
When, however, in this instance the number of fibers observed 
above the branches to the thigh at (C+S:) was diminished by 
the number observed just de/ow the branches at (S:), the 
difference was found by Dr. Dunn to be 343 (see Table XIV). 
Thus her observed number exceeded her number calculated in 
this manner by 343 fibers. This excess is explained as the 
