DIAMETERS OF NERVE CELLS AND FIBERS 541 
next to the last it appears that the ratio is a trifle smaller in 
the last than in the first group—2.08 compared with 2.18. There- 
fore the entire nerve fibers have grown in diameter a little more 
rapidly than the ganglion cells from which they arise. In the 
last column the fibers from the distal side of the ganglion are 
compared with the ganglion cells and these behave in nearly the 
same manner. As will be shown later the increase in the diam- 
eters of the axes is Somewhat more rapid than that of the entire 
fiber and the relation of the axes to the cell bodies is given for the 
fibers distal to the ganglion in table 9 (B). 
While there is a slight tendency for the ratios in table 7 to 
decrease as we pass from the first to the last groups, by far the 
TABLE 8 
Comparing the computed diameters of the spinal cord cells in albino rats of different 
sizes with the diameters of the corresponding ventral root fibers. In the last column 
are given the ratios. Data condensed from tables 2 and 6 
AVERAGE 
DIAMETERS OF 
SPINAL CORD CELLS. VE NS RATIOS 
Da eae Eaves Nee) Mere an PaaS SHiTHAL. ‘oor 
LONGITUDINAL FIBERS AT (B)  /_________— 
SECTIONS B: Sp. G. C. 
grams days 
29.0 24 24.5 10.7 he 2229 
85.1 56 27.9 DING 12220 
149.5 105 29.4 . 1: 1.90 
264.8 267 29.2 18.2 1: 1.60 
IRENMO Se alee one feel? plea 
most striking point is their similarity at allages (=body weights), 
the increase in the diameters of the cells and fibers running nearly 
parallel. 
Table 8 is based on tables 2 and 6, and gives the mean values 
for the diameters of the spinal cord cells (data from the longitud- 
inal and transverse sections combined) and the diameters of the 
largest myelinated fibers in the ventral root. In the last column 
it is seen that the relative value for the nerve cells diminishes very 
rapidly because the growth of the cell bodies in diameter early 
(56 days, chart 3) becomes very slow, while the nerve fibers con- 
