74 JOURNAL OF COMPARATIVE NEUROLOGY. 
eral thoracic nerves and found this to cause a degeneration of 
small fibers in the sympathetic trunk. He therefore concludes 
that the cell bodies of these neurones are located in the spinal 
cord. It is thus evident that as regards man we have not yet 
any satisfactory demonstration of efferent nerve fibers in the 
dorsal roots, although their existence seems possible. 
VII. The Relation of the Number of Nerve Fibers Proximal 
and Distal to the Spinal Gangha. 
On this problem we have yet no data for man. SHER- 
RINGTON (1894-5) and others make the statement that in mam- 
mals a medullated nerve fiber in the periphery branches little or 
not at all except near its termination. Harpesty (1899 and 
1900)’, and others have shown that in the frog the number of 
nerve fibers distal to the spinal ganglia is greater than the 
number in the dorsal and ventral roots combined. Ac- 
cording to Dunn (1g00)”, in the frog about 6 to 8% of 
all the fibers in the mixed nerves which innervate the 
thigh divide; and according to her results on the frog, pub- 
ished in 1902”, in the mixed nerves; about 9-10% of the 
fibers to the thigh and about 21-22% of the fibers in the shank 
divide. That nerve fibers may divide at places where the 
nerve trunk gives off no branches is also demonstrated by her 
work, 
For our calculations, however, it is immaterial whether or 
not an afferent fiber branches, because the relation which we 
shall try to establish is one between the area of the dermal 
surface and the nerve fibers at a place where they are /east nu- 
merous, i. e., in the dorsal roots. Even if there should be a 
distal excess due to some other cause than distal branching, 
and even if the fibers which form such an excess should be 
pathways for afferent impulses, yet the dorsal roots would still 
constitute the only pathway by means of which these afferent 
impulses could reach the spinal cord. 
