306 CHI PING 
In her studies on inbreeding, King (’18) states that the closest 
form of inbreeding, continued for many generations, has not 
caused a diminution in the average body weight of the inbred 
rat at any age, and that through the selection of the largest and 
most vigorous animals for mating, inbred rats are superior in 
body size to the stock animals reared under similar environmental 
conditions. Nevertheless, our data as they stand indicate that 
in the inbred rats the largest cells in this ganglion are clearly 
smaller in size than in the standard strain. It seems best not to 
comment on this relation until studies have been made on the 
wild Norway, and these I hope soon to undertake. 
SUMMARY 
A. Based on the data for the ‘standard’ strain 
1. Between birth and maturity the largest cells in the superior 
cervical sympathetic ganglion increase about 55 per cent in 
diameter, while the increase in the nuclei is less than half of this 
amount. 
2. The growth occurs in two phases: the first phase of rapid 
growth ends at about twenty-five days and the second phase of 
less rapid growth continues to the end of the record. The present 
data do not show a marked alteration in rate at puberty. 
3. The size of these cells is more closely related to the body 
weight than to the age of the rat, but there is a marked tendency 
after puberty for the females to have slightly larger cells than 
the males of the same age. 
4. The nucleus-plasma ratio increases from 1 to 4 at birth to 
about 1 to 12 at maturity. 
5. At maturity the large cells may be classified in three groups: 
1) those with Nissl bodies accumulated at the periphery of the 
cell; 2) those with large masses of Nissl bodies accumulated 
around the nucleus; 3) those with larger Nissl bodies mingled 
with small ones, and more or less evenly distributed within the 
cell. Moreover, a few binuclear cells are found, and in the older 
rats some pigmented cells are present. 
