518 Cc. A. STEWART 
(a, a’, newborn control; b, b’, test rat). As compared with the 
control of the same body weight, not only the various subdivi- 
sions weighed, but also the olfactory tracts, tuber cinereum, 
corpora quadrigemina, and especially the para flocculi are evi- 
dently much larger in the starved rat. 
Although considerable brain growth thus occurs during mainte- 
nance of constant body weight in young rats, nevertheless it 
occurs at a greatly retarded rate in comparison with the normal 
growth during the corresponding period of time. This is so 
well shown in figure 1 (6, b’ and c, c’) that a lengthy discussion 
is unnecessary. 
TABLE 3 
Comparison of relative intensity of growth of various parts of the brain in normal 
and test rats 
PERCENTAGE BY WHICH THE WEIGHT OF THE 
VARIOUS PARTS OF THE BRAIN 
At 11 days es that |At 3 weeks exceeds that 
at birth in normal 10-gram rats 
Normal Test Normal Test 
@erehellluinmve... eee ss Gece cee 696 272 274 113 
ACCOR, WS. | Ge. Gk olen seis eee eam 351 240 144 30 
Gere rue oe a eee eae mne 293 131 85 29 
STAT SETI Ge pee ae ears 130 (2 63 20 
In older rats held at maintenance for various periods, investi- 
gators in general have noted practically no change in the brain 
weight. Thus Hatai (’08) found the brain weight in stunted 
rats to be practically identical with that for normal younger 
rats of the same body weight. In a large series of rats studied 
by Donaldson (’11), after maintenance from 30 to 51 days of 
age, the brain exceeded the calculated initial weight by only 3.6 
per cent. Jackson (’15 a) and Stewart (’16) conclude that 
there is practically no change in the weight of the brain in rats 
held at maintenance for various periods starting at 3 weeks of 
age. Holt (’17) noted a slight increase in brain weight in under- 
sized rats fed upon an unsuitable diet of whole corn after the 
period of weaning. | 
