302 CHESTER A. STEWART 
for considerable periods, nevertheless, certain organs and parts 
of the body having a very strong growth tendency continue to 
increase in weight, other organs and parts with a weaker growth 
capacity remain nearly unchanged, while still other parts suffer 
a loss in weight (Jackson ’15 b and Stewart 716). These changes 
were observed chiefly in rats whose underfeeding began at the 
age of three weeks and terminated at the age of ten or twelve 
weeks. Very few observations have been recorded, however, 
concerning such changes which may occur either in younger 
animals subjected to inanition for various periods, or in animals 
underfed for much longer periods. An investigation was there- 
fore undertaken in order to determine these changes. The work 
was done in the Institute of Anatomy of the University of Minne- 
sota, under the supervision of Dr. C. M. Jackson, to whom I am 
indebted for valuable aid and direction. 
MATERIAL AND METHODS 
For the present investigation eighty-nine albino rats (Mus 
norvegicus albinus) were used (table 1), all of which were autop- 
sied at the close of the experiment. They included thirty-four 
controls and fifty-five test rats. . 
From the litters used, the controls were selected at the begin- 
ning of the experiment, the sex being determined according to 
the method of Jackson (’12). Seven (4 M, 3 F) of the controls 
were killed and autopsied when they had reached (on full feeding) 
an approximate average net body weight of 10 grams, four (. M, 
1 F) at 13 grams, fourteen (7 M, 7 F) at 15 grams, one (M) at 27 
grams, one (F) at 40 grams, four (2 M, 2 F) at 50 grams, and 
three (2 M, 1 F) at 70 grams. Whenever possible, the controls 
were selected from the same litters as the test rats. In some 
instances, however, this was not possible, especially in the case 
of the controls for the rats underfed for very long periods. 
The majority of the test rats were starved for intermittent 
periods starting a short time (24 to 48 hours) after birth, and were 
killed (by chloroform) and autopsied at the age of three weeks 
(17 rats; 9 M, 8 F), six weeks (9 rats; 6 M, 3 F), and ten weeks 
