Donatpson, Law of [nunervation. 227 
obtain the corresponding data for the areas of skin, —in accord- 
ance with which the afferent fibers are to be distributed. 
(3) On the relative areas of the skin of the thigh, shank, 
and foot. 
Since the relative weights of the muscles in the several 
segments of the frog’s leg remain unaffected by the size of the 
frog (DonaLpson, 1898, and DonaLpson and SCHOEMAKER, 
1900), and since the conformation of the leg is similar in large 
and small frogs, it follows that the relative areas of the skin 
covering the different segments of the leg are unaffected by the 
absolute size of the frog examined. This removes the neces- 
sity of always working with frogs of the same size. 
My acknowledgments are due to Dr. Dunn for working 
out the area of the skin in the several segments of the frog’s 
leg. As the method used was somewhat novel, it will be nec- 
essary to describe it in detail. 
The frogs examined had the following body measurements: 
TABLE VI. 
Frogs examined for area of skin. 
Length from tip of nose to 
Frog No. Body Weight, grams. end of longes !toe. 
g y ght, ¢ g 
I 34.76 190 mm. 
Zz 36.75 195 mm. 
B 28.17 187 mm. 
The procedure was as follows: The frog was killed with 
chloroform and pinned out on a sheet of cork with the ventral 
aspect uppermost. One leg was extended and abducted so 
that it made an angle of about forty-five degrees with the longi- 
tudinal axis of the body. A strip of glass about 3 cm. wide 
and a few centimeters longer than the frog’s leg, was then 
passed beneath it. The leg thus rested on this strip of glass 
and was in turn covered by a similar strip of the same size. 
On the upper surface of the latter a layer of tracing paper had 
been fastened by a drop of paste at each of the four corners. 
Rubber bands were next passed over the two strips of glass 
and the leg lightly compressed between them. Before putting 
on the covering strip, however, the foot was stretched so as to 
