WEIGHTS OF UNDERFED YOUNG ALBINO RATS 335 
and also in adult rats subjected to acute and chronic inanition 
Jackson (15a, ’15 b) found the percentage weight of the heart 
to remain practically unchanged. Apparently the effects were 
less marked than in my experiments, in which the underfeeding 
was begun earlier, or carried over longer periods. 
LUNGS 
As compared with the Wistar norm for rats of corresponding 
body length, the weight of the lungs (table 2) appears to be 
unusually high in my. young controls. For the largest group 
(14 rats, 7 males and 7 females, 13 days old) weighing about 15 
grams, the average absolute weight of the lungs (sexes combined) 
is 0.234 gram, as compared with the Wistar average of 0.166 
gram for rats of corresponding body length. 
Jackson (’13) found the normal weight of the lungs in the rat 
at one week to average 0.1938 gram, with which my average of 
0.1995 gram for controls of the same age agrees closely. It 
appears, therefore, as pointed out by Jackson (’13), that weights 
for the lungs derived from Hatai’s formula appear much lower 
than the actual observed values in very young rats. 
As compared with my controls, the average weight of the lungs 
is low in the test rats at three, six and ten weeks of age, the 
decrease in each case amounting to a loss of approximately 26 
per cent (subject to slight correction for difference in body weight). 
In the longer experiments the lungs average heavier for the 
underfed rats than in the controls, with the exception of one 
female at 139 days. The presence of lung infection among the 
older underfed rats probably accounts in part at least for the 
increase in the weight of the lungs. The data for the test rats 
weighing about 70 grams after very long fasting also include the 
weights of the lungs for five rats which were asphyxiated. In 
these instances the weights would no doubt be high due to the 
greater amount of blood retained in the lungs. Therefore the 
effect of the very long fasting period upon the weight of the lungs 
is doubtful. 
Jackson (’15 b) found that in young rats subjected to main- 
tenance for various periods, the lungs show a slight decrease in 
