142 ELIZABETH HOPKINS DUNN 
teen days and with a body weight of 278 grams. However, his 
curve immediately drops to a number not exceeding by one fiber 
the record for a male of seventy-seven days and 213 grams body 
weight. Tozer and Sherrington (710) argue that the oculomotor 
is a mixed nerve. 
Ranson (’08) made a few records for the number of ventral 
root medullated nerve fibers of the second cervical nerve in the 
albino rat in order to show the ratio of ventral to dorsal root 
nerve fibers. While his records for the dorsal roots begin with 
twelve day rats his counts for the ventral root fibers are only for 
seventy-two day and six month rats. The level of the count, the 
weight and sex of the rat are not stated. 
His records for the dorsal root fibers give no stage between 
twelve and seventy-two days but show a marked increase in 
number at the later age. Of the ventral root fibers the average 
number of fibers for four seventy-two day rats is six hundred 
and thirty-two while that for two six month rats is seven hundred 
and thirty-six fibers. My own averages for seventy-five day rats 
and nine month rats give six hundred and fourteen fibers for 
seventy-five days against six hundred and ninety-seven fibers 
for the nine month rats. 
Ranson’s records then are comparable with those presented 
now and together they show that in regard to the second spinal 
nerve of the albino rat the number of medullated nerve fibers in 
both the dorsal and ventral nerve roots increases during the life 
of the individual but that the greatest increase occurs before the 
sexual maturity or so-called puberty of the animal. 
More than this, if comparison between Ranson’s records for 
the dorsal roots and my own records for the ventral roots of other 
individuals is permissible, the statement is possible that the in- 
crease in number is relatively greater and extends over a longer 
time among the dorsal root nerve fibers than among the ventral 
root nerve fibers. The functional significance of this finding is 
not so great as it would be if the counts for the dorsal root fibers 
had been made peripheral to the ganglion when the fibers directly 
innervating sensory elements would have been counted. As it 
is, the records are for processes central to the ganglion and ending 
