SYMPATHETIC CELLS: NORWAY RAT 317 
C. In relation to observed age 
The rats with known ages form a separate series for the pres- 
ent discussion. The computed diameters of the cells and the 
nuclei are given in table 3 according to age. Examination of 
the table reveals that the cells and nuclei grow comparatively 
fast during the first twenty-five days of life. In order to show 
the contrast between the early growth and that which follows, 
data selected from table 3 have been arranged in table 4. 
10 
SORE eeReeee 
Se Body length—mm. 
50 100 150 200 250 
Chart 2 Based on table 2 and giving the computed diameters of the cells 
and their nuclei according to sex—on body length in millimeters. Wild Norway 
rat. Males Females ---------- 
Table 4 shows that at the end of twenty-five days the cells 
and the nuclei have increased in diameter 1.31 and 1.14 times, 
respectively, for the male, and 1.48 and 1.25 times for the female; 
while the increase from 25 days to 134 days—a period which 
is more than five times as long—is 1.19 for the cells and 1.21 
for the nuclei of the male and 1.04 for the cells and 1.06 for the 
nuclei of the female. 
The graphs in chart 3 illustrate the fact that during the first 
twenty-five days there occurs a sudden and rather irregular 
increase, which is followed by a slow advance. No clear indi- 
cation of a difference according to sex is to be seen. 
