548 HENRY H. DONALDSON AND G. NAGASAKA 
peroneal nerve from the albino rat the value of the area of the 
axis as 53.7 per cent and at the distal end of the same nerve the 
value of 49.9 per cent. The mean body weight of the rats was 
135 gms. In another series of studies, Greenman (’17) has 
found the area of the axis about 40 per cent in a series of thirty 
peroneal nerves from fifteen animals, all about 151 days of age. 
In both these series the fibers were projected, outlined, and then 
measured with a planimeter. In the cases where the sheath was 
wavy this method would give a somewhat greater area for the 
sheath than would be determined by direct micrometric measure- 
TABLE 12 
Giving the relations of the spinal ganglion cells and their nuclei. In the last 
column appears the ratio of the volume of the cytoplasm (the volume of the entire 
cell less the volume of the nucleus) to the volume of the nucleus. Data condensed 
from table 3 
NERVE CELLS NUCLEI 2 
pei AVERAGE i fen 6 Se eee Cane curondinae 
WEIGHT Mere Mean Ratio of Mean Ratio of LORVOLU MEO: 
diameter jenlargement| diameter {enlargement RE 
grams days BK mn 
29.0 24 M3) 3) 1.00 11.9 1.00 ILE 70, 
85.1 56 29.8 1.29 14.8 1.24 7-216 
149.2 105 33.4 1.42 15.9 1.34 Sane 
264.2 267 38.1 1.62 18.0 | 151) 1: 8.48 
ment, and thus. contribute to giving a low percentage for the 
area of the axis, as it appears in the last 1917 series. 
We may conclude from Dunn’s record and our own that there 
is a growth in the relative area of the axis up to about 250 to 300 
days and that the axes in the fibers of the ventral nerve roots of 
the spinal nerves have 50 per cent of the area of the fiber at 
this age, when the measurements are made with the eyepiece 
micrometer. 
ON THE NUCLEUS-PLASMA RELATIONS 
In the spinal ganglion cells here measured the mean diameters 
of the cell bodies and of their nuclei are given in the condensed 
table 12, and the ratios of the volume of the nucleus to that of 
the cytoplasm (= cell volume less nucleus volume) have been 
