532 HENRY H. DONALDSON AND G. NAGASAKA 
From the material as represented in figure 1, the following 
series of cross-sections of myelinated fibers fixed in osmic acid 
were obtained: 
At A, in the seventh cervical nerve close to the ganglion. 
At B, in the ventral root. , 
At C, in the dorsal root. 
Also, the following sections of nerve-cell bodies from material 
fixed in Bouin’s fluid: 
At 1, a longitudinal section of the spinal ganglion. 
At 2, a transverse section of the spinal cord. 
At 3, a longitudinal frontal section of the spinal cord (in the 
plane of the rectangle—fig. 1). 
In the sections from A, B and C, the fibers were cut as nearly 
as possible at right angles to their long axes, which made the 
cross-section of a myelinated fiber nearly circular in outline. 
In this ease but a single measurement of the diameter of the entire 
fiber and of the axis, respectively, was made. For measurement 
a Zeiss ocular no. 6 and oil-immersion ob]. 2 mm. were used with 
the micrometer eyepiece having each division equal to 2u. 
Ten of the largest fibers in a single section were thus measured 
for each locality. 
In the case of the nerve cells, more measurements were neces- 
sary because, in the first place, the outline of the cell bodies is not 
circular, and, in the second place, it was necessary to measure the 
nuclei also. 
In the case of the spinal ganglion cells the two maximum diam- 
eters at right angles to each other were determined, while one 
diameter alone was taken for the nucleus. 
In the case of the spinal cord cells the longitudinal diameter 
was the longer one, passing through the long axis of the cell and 
at right angles to the transverse or short diameter which was 
measured through the middle of the nucleus. This is similar to 
the method described by Hardesty (’02). Here again, but one 
diameter of the nucleus was measured. In each instance the 
largest cells in a given section were those measured. These 
series of measurements taken on the fibers at A, B, and C, and 
on the cells at 1, 2, and 3, furnish the data that are to be consid- 
