SYMPATHETIC CELLS: NORWAY RAT a2] 
aldson (711) the percentage of water in the central nervous system 
of the Albino and Norway rat at like ages is nearly the same, 
so the ages of the Norway rats whose percentages of water are 
known may be obtained from table 74 of ‘The Rat’ (Donaldson, 
15) and the growth of the cells as shown in chart 4 can be trans- 
lated into age. Using this procedure, the curves in chart 4 
represent the gradual growth from twenty-five days of age 
to maturity. 
ae ees 
BEE Eero 
aan RENE ns es 
20 PRBEECECEEEEE EEE ei 
a Fa Oca Fo a BD 
REPOS eeeh sae 
SE ete EH 
se canuasaunaseeeneedaas 
Poo Snes ees eee eee eee ee 
is spauece 
81 80 19 78 it 16 
Chart 4 Based on table 5 and giving the computed diameters of the cells 
and their nuclei according to sex—on percentage of water in the brain. Wild 
Norway rat. Males Females ---------- 
The examination of table 5 enables us to see that in general 
the female has a slightly higher percentage of water in the brain 
than the male, due probably to the smaller absolute size of the 
brain (Donaldson, ’16), but the cells of the male exceed in diam- 
eter those of the female in seven out of eight cases. 
MORPHOLOGY OF THE LARGE CELLS 
The general morphological changes in the large cells from 
birth to maturity are similar to those in the cells of the Albino. 
The large cells of the first few days are much alike in the two 
forms. The distribution of Nissl granules and the tendency to 
accumulate at different regions in the cell in the later ages are 
also alike in the two forms. There is, however, some difference 
