18 JouRNAL OF COMPARATIVE NEUROLOGY. 
TABLE V—Showing the small and large fibers separately in dorsal and ven- 
tral regions of spinal nerve of Frog (Rana virescens)—After HARDESTY. 
In the following table, Sec. 1 and Sec. 3, mean the two different levels of sections, 
Small fibers are those 5 / or less in diameter 
Nerve Fibers |Sec) 1|Sec. 3] -Dif- 
Small | 155 | 164 i 9 
III N Boe Large | 162 165 3 
a ei: Small | 306 | 289 17 
Large gI 90 I 
f Small 193 203 Io 
ihe Dors 1 Large 95 96 : 
Waut Small 45 29 6 
Large 88 88 fe} 
Small | 107 95 126 
VIIN. { Vent. fideeen 28h she " 
As the above table shows, the small fibers in some nerves 
are more numerous than the large fibers. It seems very prob- 
able that some of the small cells are still in an immature condi- 
tion and have not yet sent off an axone, If this is true, then 
there must be a greater number of these small cells than is rep- 
resented by small fibers in the nerve root. 
From this numerical relation, it seems to me that small 
cells are in an immature or growing stage. 
to be true in another way. 
This can be shown 
The writer gave a hint in the pre- 
ceeding pages that the small cells show a tendency to shrink 
readily. We know that a cell-body which contains much water 
is harder to preserve in a normal state than the cells with less 
water. The cells with more water show more shrinkage. It is 
already known that the animal body contains when young com- 
paratively a greater quantity of water than the mature animals. 
I am allowed to quote from some unpublished observations 
of Dr. Donatpson on the white rat at birth and at maturity 
which show the following percentages of water in the central 
nervous system. 
TABLE VI—Percentage of water in white rat at different ages—After 
DONALDSON. 
Age Brain Spinal Cord 
Birth 87% 85% 
Maturity 78% 72% 
