WEIGHTS OF UNDERFED YOUNG ALBINO RATS 309 
with the Wistar norm tables of Donaldson (15). By this means 
it was possible to detect any marked variations from the normal 
in my control rats. For purposes of convenient comparison, 
the weights of organs from the Wistar tables for normal rats of 
body length corresponding to my controls have been inserted in 
table 2. In general, it will be noted that both the body weight 
and the corresponding organ weights are slightly higher in my 
controls than in the Wistar tables. If the comparison were based 
upon body weight rather than body length, there would usually 
be much closer agreement. While body length is a satisfactory 
basis for comparison between my controls and the Wistar data, 
it cannot be used in the case of the test rats, for as will appear 
later, the body length in underfed rats continues to increase even 
when the body weight is held constant. Body weight therefore 
was selected as a basis for comparison between my controls and 
test rats, since it can easily be held constant, which is not true 
for the body length. 
In the present paper, for the most part only average data are 
published. However, a copy of the original individual observa- 
tions will be deposited in The Wistar Institute of Anatomy and 
Biology, Philadelphia, where they may be consulted by those 
interested. 
The normal variability of the various organs makes it necessary 
in some cases to exercise considerable care in drawing conclusions 
from the relatively limited number of observations. Never- 
theless, the data appear sufficient to establish fairly accurately 
some of the more obvious and important changes due to the 
experiment. 
An abstract of that part of the present investigation dealing 
with the underfeeding of the rats from birth to three, six and 
ten weeks of age was published in the Proceedings of the Ameri- 
can Association of Anatomists, New York meeting, December, 
1916 (Stewart, 717). 
