524 Cc. A. STEWART 
Thus the olfactory bulbs appear relatively larger in the stunted 
rats than in normal rats of the same brain weight. 
For the group fasting three weeks the relative increase is slight 
and inconstant. In the normal rats with corresponding brain 
weight (0.6309 to 0.8837 gram) the relative weight of the olfac- 
tory bulbs is likewise nearly stationary, though somewhat var- 
iable. This is in agreement with Holt (’17), who found the rela- 
tive proportions of the olfactory bulbs to remain practically 
unchanged in rats undersized after four and eight weeks of feed- 
ing upon an unsuitable diet of whole corn. 
The data for my rat underfed from birth to eight weeks indi- 
cate an apparent increase in the relative weight of the olfactory 
bulbs, which is in accordance with the general tendency toward 
an increase in the relative size of olfactory bulbs in normal rats 
with brains of corresponding weight. Miss Holt noted a tend- 
ency for the bulbs to increase in relative weight during pro- 
longed defective feeding in rats weighing about 50 grams. 
On the whole it therefore appears that during the persistent 
growth of the brain in underfed young rats the olfactory bulbs 
tend to maintain a relative size similar to that in the normal 
brain of corresponding weight. In the youngest and smallest 
group, however, they apparently become relatively hypertro- 
phied and appear relatively larger than in normal animals with 
the same brain weight. 
DISCUSSION 
Quite uniformly the results of experiments have shown that 
the brain demonstrates a marked ability to grow when increase 
in body weight is prevented by underfeeding only in very young 
animals and at a time when the normal growth of the brain is very 
pronounced. There is, therefore, apparently a definite relation 
between the increase in size accomplished during starvation and 
the normal growth power possessed by the organ at the time 
when underfeeding is commenced That this dependency upon 
the intensity of the growth impulse applies also to the various 
parts of the brain is evident upon comparison of the relative 
rapidity of growth of the various parts of the brain in young rats. 
