WEIGHTS OF UNDERFED YOUNG ALBINO RATS 319 
a lipoid-free ration to exceed slightly the length given by the 
Wistar reference tables for normal rats of corresponding body 
length. Also in a later personal communication to Prof. C. M. 
Jackson he stated that in rats subjected to chronic inanition the 
tail becomes relatively long. 
Harms (’09) observed that while starvation produced a marked 
decrease in the body length of Triton, the tail length remained 
practically unchanged. Morgulis (11) however found the con- 
verse to be true in Diemyctylus. 
Jackson (715 a) found that acute and chronic inanition in adult 
albino rats also tends to produce relatively long-tailed individuals, 
due probably to a shrinkage in the trunk length. 
HEAD 
In the test rats underfed from birth to three and ten weeks of 
age, the absolute weight of the head (table 1) is slightly higher 
than in the controls of corresponding body weight. In the test 
rats at three weeks of age there is an appa) nt increase from 
an average of 2.42 grams for the younger controls (sexes com- 
bined) to 2.83 grams, an increase of approximately 16 per cent 
(uncorrected for shght difference in body weight). The in- 
crease in head weight at this age is due in large part to the increase 
in the weight of the brain. At ten weeks of age, the increase of 
the head weight in the test rats (about 4 per cent) is very slight. 
At six weeks of age, the weight of the head for the underfed in- 
dividuals (3.27 grams) is slightly lower than the average for the 
younger controls (3.40 grams). In the rats underfed for very 
long periods the weight of the head exceeds that in the controls 
16 to 26 per cent. 
In general, therefore, the data indicate that in very young rats 
underfed for considerable periods, the weight of the head slightly 
exceeds that of the younger controls of corresponding body weight, 
especially after very long periods of underfeeding. 
Jackson (715 b) similarly found in the majority of instances 
the head apparently to increase slightly in weight in young rats 
kept at maintenance for various periods. In adult rats subjected 
to both acute and chronic inanition Jackson (’15 a) found the 
