256 JouRNAL OF COMPARATIVE NEUROLOGY. 
number given by the formula must be increased by a certain 
percentage of itself: 
For the Thigh by 5.0% 
For the Shank by 18.0% 
For the Foot by 21.8% 
4. When due allowance is made for the splitting fibers, 
it is found that the agreement between the estimated and 
observed numbers is close: 
Difference. 
oye NSN NGS average of 6 cases = +1.10% 
Rorthershankse2 oe asee= average of 2 cases = — .28¢ 
ForathesHootees=—— pee average of 2 cases = 
*The necessary observations for the foot are lacking, though the agree- 
ment would probably be close there also. 
5. Some of the afferent fibers are distributed to the 
muscles. The proportion in the thigh is highly variable. The 
one case available shows a larger proportion of afferent fibers 
to the muscles of the shank than to those of the thigh, sug- 
vesting that in the foot the proportion would be still greater. 
Thus, while the number of afferent fibers in a segment 
appears to be in proportion to the area of the skin, yet the 
distribution of these fibers is both to the skin and the muscles. 
The significance of this arrangement can only be determined 
by work on other forms, both higher and lower than the frog, 
in the zoGlogical scale. 
BIBLIOGRAPHY. 
Date, H. H. 
19g0t. Observations chiefly by the Degeneration Method, on possible 
Efferent Fibers in the Dorsal Nerve Roots of the Toad and Frog. 
Journ. of Phystol. (Foster). Vol. XXVII, tgor. 
Donaldson, H. H. 
1898. Observations on the Weight and Length of the Central Nervous 
System and of the Legs, in Bull-frogs of Different Sizes. Journ. 
Comp. Neurol. Vol. VIII, No. 4, Dec. 1898. 
Donaldson H.H. and Schoemaker, D. M. 
1900. Observations on the Weight and Length of the Central Nervous 
System and of the Legs in Frogs of Different Sizes (Rana virescens 
brachycephala, Cope). Journ. Comp. Neurol. Vol. X, No. 1, 
Feb. 1900. 
