206 CAROLINE M. HOLT 
ner. The brain was placed, ventral side down, on the dissect- 
ing board. Then with a thin, sharp scalpel held in a position 
perpendicular to the plane of the board and at right angles to 
the plane of the median longitudinal fissure, the bulb wassevered 
just below the anterior limit of the cerebrum.? The bulb, with 
the remainder of the brain was then placed in a covered weighing 
bottle and the weight of both the entire brain and of the severed 
bulb ascertained. 
The final controls were weighed and placed under the normal 
living conditions of the colony: 1.e., housed, in long wooden 
cages with wire fronts, thick shaving-covered floors, and paper 
nests, and given plenty of fresh water with a carefully super- 
vised scrap diet. The test rats were weighed and placed in 
adjoining cages under exactly the same conditions as the final 
controls, save for the diet. The food given the test rats con- 
sisted of an unlimited amount of whole corn, usually fed on the 
cob, save in case of very young animals, or those weak from a 
long period of underfeeding. In such cases, the corn was shelled 
as the animals were not able to remove a sufficient amount for 
themselves. 
Both control and test animals were weighed from time to 
time and the weights recorded. Note was also made of any 
irregularities, such as a temporary change in diet, etc. 
At maturity, a certain number of test and of control animals 
were mated in order to find out whether underfeeding affected 
the fertility of albino rats. 
In the case of relatively small litters in which the members 
were usually well grown and in good physical condition when 
weaned—and especially if weaning was delayed until the rats 
were four weeks old—it was possible to keep the test animal on 
a corn diet for a month or more with practically no difficulty. 
2 Small bulbs tend to differ characteristically in shape from large ones. On 
section it is seen that the cap of gray substance extends somewhat further 
caudad on the ventral surface of the small bulb than it does in the case of the 
large bulb. The weight of gray substance thus lost in the case of the small bulb 
is a very small fraction of the total weight of the bulb but a much larger fraction 
of the gray cap. Care must, therefore, be taken to include this portion when 
the number of cells of the gray substance is to be detérmined. 
