SECOND CERVICAL NERVE OF THE RAT 147 
series was considerably increased by the handling of very young 
material. 
These measurements prove the increase in the size of the largest 
medullated nerve fibers, but that the increase is not confined to 
the largest fibers is evident to one making even a casual study of 
Oo 09 od oe 
02 9000 i 0 os 2D. 00 
°0 oP 8 ob ve oO LOO 
Bo Me2310 RoE O 0°60 
SO Sig 8 508 oO 0 
A B Cc 
Fig. 3 Camera lucida drawings by A. B. Stredain at table level, ocular 8, objec- 
tive 8, Zeiss, showing typical areas from the ventral roots of the second cervical 
nerve of three male rats of one litter. A at seven days, body weight 8.9 grams; 
B at fourteen days, body weight 21.93 grams; C at one hundred and thirty-eight 
days, body weight 260 grams. 
“0 
8 
oO Be 
96 OQ: 200 00 
D E 
Fig. 4 Camera lucida drawings, at same magnification as those of fig. 3, show- 
ing typical areas from the ventral root of, the second cervical nerve of two male 
rats. Dat 270 days, body weight 349 grams; E at 640 days, body weight 414 grams. 
the material. Fig. 3 was drawn by camera lucida to include 
typical areas from the ventral roots of the second cervical nerves 
of three male rats from one litter. A at seven days, B at fourteen 
days and C at one hundred and thirty-eight days. Fig. 4 gives 
drawings at the same magnification from two additional male rats, 
D at two hundred and seventy days, and # at six hundred and 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 22, NO. 2 
