SYMPATHETIC CELLS: ALBINO RAT 285 
the age of eighty days (body weight about 100 grams) which is 
the period of puberty (Donaldson, ’15, The Rat, p. 21) there 
appears a tendency for the cells to be larger in the female than 
in the male. It will be noted, however, that at the age of eighty- 
nine days, and also at 250 days, the male exhibits larger cells than 
the female of the same age. This discrepancy is explained when 
we take the body weights of the males into consideration. As 
given in table 1, the body weight of the male rat eighty-nine days 
old is twice that of the female of the same age, and the dis- 
crepancy is even greater in the case of the male at 250 days. 
These males should be expected to have larger nerve cells by 
virtue of their body weight, and when a correction is made for it, 
the values for the male cells should fall below those for the female 
at these ages also. In. general one may say that the female, 
after reaching puberty, has these cells larger than the male, if 
the body weight of the male does not too greatly exceed that of 
the female. As regards the nucleus, however, chart 1 exhibits 
a less clearly marked sex difference. 
The fact that there is a better growth of the cell bodies in the 
female is more clearly illustrated in chart 2, in which graphs for 
the diameters of the cells and nuclei have been plotted on body 
weight. From birth to the time just before puberty, the varia- 
tions in the growth of these cells in the two sexes are similar to 
those shown in chart 1. 
Just before puberty, when the rat weighs about 60 grams, the 
female becomes gradually more advanced in the growth of these 
cells and overtakes the male of the same body weight. The 
growth of the nerve cells in the female also shows a more regular 
course than that of the male. The growth of the nuclei at the 
corresponding ages of the two sexes follows in the same manner 
as that of the cell bodies, although the difference is relatively 
small. 
It is proper to keep in mind, however, that when the compari- 
son is made on the basis of body weight, the female is normally 
the older, and, further, that in several other growth changes the 
female tends to be precocious; both of these influences would 
tend to produce larger cells in the female under these conditions. 
