16 JOURNAL OF CoMPARATIVE NEUROLOGY. 
greater number of fibers than are found in a section of the 
trunk further distal. 
‘s, The decrease in the number occurs among the smaller 
fibers of the nerve. 
‘6. The general explanation of these relations is found 
in the fact that the fibers arising from the spinal ganglion grow, 
on the one hand, toward the spinal cord by way of the dorsal 
root and, on the other hand, toward the periphery by way of 
the nerve trunk; and, that the fibers of the ventral root grow 
from the spinal cord towards the periphery. 
“7, In frogs of increasing weight, the fibers of the dorsal 
root increase in number more rapidly than do those of the 
ventral root.” 
From the investigations of the above named authors it is 
evident that the number of cells in ‘the spinal ganglia is 
greater than the number of fibers in the corresponding dorsal 
nerve root. This is true for the mammal represented by the 
rabbit, as well as for the frog. Further, Harpresty has shown 
in the case of frog that fibers in the dorsal and ventral nerve 
roots, as well as in the nerve trunk, are distributed in different . 
levels as though nerve fibers were continuously growing out 
from ventral horn cells on one hand and the spinal ganglion 
cells on the other, and he interprets his results as indicating 
growth. In mammals, however, Date’ was unable to find this 
indication of growth in the mature cat. If this arrangement in 
the cat should prove to be constant, the difference between the 
cat and the frog might be explained by long continued growth 
changes in the frog as compared with very rapid enlargement 
of the cat to a fixed size. Besides the excess of the cell- 
bodies in the spinal ganglion of both frog and rabbit and evi- 
dence of the growth changes in the frog, we have our own ob- 
servation that the smallest and smaller ganglion cell-bodies are 
in the white rat most numerous and LENHOSSEK reports the 
same for the dog, and BUEHLER for the frog. 
1 DALE—On some Numerical Comparisons of the Centripetal anc Centri- 
fugal Medullated Nerve Fibers arising in the Spinal Ganglia of the Mammal, 
Journ, of Physiology (FOSTER), Vol. XXV, No. 3, 1900. 
