238 CAROLINE M. HOLT 
This is the part of the bulb which is weighed, and since all bulbs 
are removed in the same way, it has been assumed that we have 
corresponding portions for comparison. Because the recorded 
weights represented only this portion of the bulbs, it seemed 
advisable at first to compare the cell elements of these parts only. 
Accordingly cross sections of the bulbs were made but unfortu- 
nately, as appeared later,most of the test series were not complete 
for the portion of the gray substance beneath the hemispheres. 
The method of meeting this difficulty will be described later. 
2. Methods of study 
The study of sections was made largely with the aid of the 
Edinger projection apparatus. Cell counts were made by pro- 
jecting the sections onto white wrapping paper, outlining the 
area, and punching the image of each cell nucleus with a tally- 
ing register fitted with a sharp prong in place of the usual blunt 
register arm (Hardesty ’99). The hole punched by this prong 
insured against counting the same cell twice. It also left a 
permanent record of any particular region which could be re- 
examined later. In some cases the count for each section was. 
recorded; in others, the whole number of sections to be counted 
were registered consecutively and no record made until the end. 
Occasionally a section was recounted—to serve as a check on the 
work. 
IV. GENERAL DIFFERENCES IN SIZE 
Most of the comparisons of size and the determinations of 
cell number have been made on bulbs stunted by a defective diet, 
and on their respective controls. Only two bulbs of the exercise 
series have yet been examined. 
The general differences in size between young and mature, 
stunted and normal olfactory bulbs are very well illustrated 
by the sections shown in Plates 1, 2, and 3. Figure 1 of plate 1 
is a camera drawing of a median sagittal section through the 
bulb of a rat stunted by feeding for thirty-one days on a corn 
diet. The body length was 138 mm.; brain weight, 1.547 grams 
and the weight of the corresponding bulb which was removed and 
