224 JouRNAL OF CoMPARATIVE NEUROLOGY. 
With the exception of the data called for under (3), the 
facts needed were to be found in papers already published from 
this laboratory. We shall take up the points in the order just 
given. 
(7) The relative number of medullated ventral and dorsal 
root fibers in the nerves supplied to the leg. 
The nerves sending fibers to the leg are the VII, VIII and 
IX spinal nerves as usually numbered, or, according to the 
recent numbering of Gaupp (1897), the VIII, IX and X. 
According to the enumeration of the medullated nerve 
fibers in the dorsal and ventral roots of these nerves by Har-. 
DESTY (1899, p. 84), the proportion is. 
TABEEGE: 
Relative number of fibers in roots, 
Ventral. Dorsal. 
Frog weighing 48 grams 100 177 
ie te 59 grams 100 175 
The average of these two observations gives therefore 100 
ventral root fibers to 176 dorsal root fibers, and this is the ratio 
here employed. Such being the relation found in the spinal 
roots, it is assumed to be the same in the sciatic and crural 
nerves at the point where they enter the leg. Whatever the 
number entering of fibers the leg, they are then to be divided, 
as motor and sensory, in the above proportion. 
In this calculation no correction for possible efferent fibers 
in the dorsal roots is attempted, for we have no data with 
which to work. When efferent fibers appear in the dorsal 
roots of the frog, there is indirect evidence that the number 
must be quite small, and they are here neglected (HortTon- 
SMITH 1897, Wana 1898, Date 1901). The ventral root is 
assumed, therefore, to contain only motor or efferent fibers 
and the dorsal root only afferent or sensory fibers. 
Having determined the proportional numbers of the 
afferent and efferent fibers, the next step is to present the meas- 
urements according to which these fibers are to be distributed, 
namely, the relative weights of the muscles and the relative areas 
of the skin in the several segments of the leg. 
