OLFACTORY BULBS OF THE ALBINO RAT vi LP 
averaging 0.037 gram, or 2.08 per cent of the total brain weight 
(table 12, group 2); while for the four females, the bulbs averaged 
0.033 gram, 1.89 per cent of the total brain weight (table 12, group 
3). For these last two groups there are no data of normal 
individuals for comparison but the percentage for the bulbs 
is strikingly low. Some unpublished data in Dr. Donaldson’s 
hands show, however, that while the relative weight of the 
olfactory bulbs tends to increase up to about one hundred and 
fifty days of age, in older rats there is a tendency to decrease so 
that some of this decrease observed in the old sick rats (groups 
2 and 3) may be due to normal age changes. But the remark- 
ably small proportional weight of the bulbs here examined is 
probably due chiefly to the effect of disease. 
In this connection may be mentioned two young rats of litter 
PR (group 2), killed at seventy days. Each had infected lungs. 
These rats came from parents with infected lungs and had lived 
since birth in a dark damp cage. One had very small unequal 
bulbs which were not weighed. The other had bulbs weighing 
only 0.019 gram or 1.30 per cent of the entire brain weight. 
This pair of bulbs were the smallest observed in the whole series 
of experiments. It seems quite evident that the bulbs are 
abnormal and quite probable that this abnormality is due to 
disease. 
5. Summary and conclusions. Defective diet experiments 
1. General bodily growth in the albino rat is arrested by an 
exclusive ration of corn which constitutes a defective diet (Os- 
borne and Mendel). 
a. The skeleton is poorly calcified and somewhat distorted. 
b. The muscular system is greatly reduced. 
The coat has the appearance of that of a young animal. 
. Functional disturbances follow the arrested development. 
. There is increasing muscular weakness. 
. An increasing palpitation of the heart. 
The animals appear cyanosed. 
Sos wa 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 27, NO. 2 
