WEIGHTS OF UNDERFED YOUNG ALBINO RATS 329 
brain in my controls is usually heavier than the Wistar norm for 
rats of corresponding body length. 
From the foregoing it is evident that in rats underfed from birth 
to three weeks of age there is a marked increase in the weight of 
the brain, whereas during the longer fasting periods (both in 
those beginning at birth and those beginning at three weeks) 
the increase is very slight. Bechterew (’95) found acute inani- 
tion in puppies and kittens to produce an apparent loss of weight 
in all of the organs, including to a slight extent the central ner- 
vous system. The greatest loss suffered by the central nervous 
system was apparently in the cerebral hemispheres, whereas the 
smallest loss was in the spinal cord. Microscopic examination 
revealed evidence of delayed medullation in fiber tracts not fully 
developed when the fasting started. 
Hatai (04) noted an apparent absolute decrease of 5 per cent 
in the weight of the brain in young rats suffering a loss of approxi- 
mately 30 per cent in body weight due to an unfavorable diet of 
starch and beef-fat. 
Later, Hatai (’08) found the brain weight in rats stunted by 
feeding upon an unfavorable diet, to be practically identical with 
that for normal younger rats of the same body weight. 
Donaldson (’11) found the weight of the brain in a large series 
of rats held nearly at maintenance from 30 to 51 days of age to 
average 7.7 per cent less than that for the full-fed controls at the 
same age. However, he points out that if comparison be made 
with the calculated initial brain weight, an increase of 3.6 per cent 
is apparent in the underfed rats. This in general agrees with 
the results of the present investigation. 
Jackson (15 b) observed practically no change in the weight 
of the brain in young rats held at maintenance for various periods 
starting at three weeks of age. My experiments started on much 
younger rats, and during a period when the brain normally shows 
a marked growth capacity. This probably accounts for the 
remarkable increase in brain weight observed for my youngest 
. group. At later periods the brain loses its earlier intensity of 
growth, which is more nearly equalled by the remainder of the 
body. During acute and chronic inanition in adult rats the brain 
loses little if any in absolute weight (Jackson’’15 a). 
