308 CHESTER A. STEWART 
The decrease in the maintenance ration noted in the young 
stunted rats is perhaps associated with the decrease in the intensity 
of metabolism which normally occurs with advancing age. Jack- 
son (15 b) suggests that during maintenance in young animals 
the amount of living protoplasm may be actually reduced, being 
replaced by water absorption, or that the food-intake may be 
more economically utilized under these conditions. He also 
mentions the decrease in body temperature as a possible factor. 
This problem is apparently of sufficient interest and importance 
to warrant a more exact and thorough investigation from the 
physiological point of view. 
Since it was found very difficult to hold the test rats strictly 
at constant body weight and keep them alive for very long periods, 
a slight increase in body weight was usually permitted. Aron 
(11), Jackson (15 b) and Stewart (16) similarly found it in- 
creasingly difficult to hold animals at constant body weight as 
the experiment progressed. 
Separate weight records were kept for each rat, the individuals 
being identified by staining the integument with an alcoholic 
solution of picric acid. The identification marks had to be 
renewed morning and evening on the very young rats, but after 
the appearance of hairs the stains were very permanent. The 
young test rats were weighed daily immediately before feeding, 
whereas the controls, and also the test rats underfed for very 
long periods, were weighed at gradually increasing intervals as 
they grew older (about once in two weeks when about three 
months of age). 
The cages used, and also the warm room in which the test rats 
were kept while fasting, have been described by Stewart (16). 
The autopsy technique employed by Jackson and Lowrey (712) 
and Jackson (’13) was used with but few modifications. The 
various organs and parts were placed in a moist chamber when 
removed from the animal, and were weighed in a closed container 
on balances accurate to one-tenth milligram (0.0001 gram). 
The data collected for the controls in this work were carefully 
compared with the published records of Jackson and Lowrey 
(12), Jackson (’13 and 715), Hatai (13 and 714), King (715), and 
