OLFACTORY BULBS OF THE ALBINO RAT 241 
a thirty-day control, and Cs, a sixty-day underfed bulb, show 
108 and 103 cells with cytoplasm. 
Although a difference in cell size appeared, there seemed to be 
little difference in numbers of cell elements in the gray layer. 
Although it is not always possible to distinguish between the 
nuclei of very small cells and possible cross sections of fibers 
under the conditions used for counting—yet the error due to 
this difficulty is probably negligible. A preliminary count was 
made of all elements, having the appearance of nuclei in the 
largest sections of the bulbs F,, C;, F;, Fs, and M:, with the 
following results. 
TABLE 1 
INITIAL CONTROL TEST FINAL CONTROL 
Bulb | Num- Bulb | Num- Bulb | Num- 
Bulb Age weight |ber cells} Bulb Age weight |ber cells Bulb Age weight |ber cells 
days grams days grams days grams 
Mie ees oO) | "0029) 2172)" By 62 | 0.020} 2569] F; 61 0.032) 2569 
C; 59 | 0.021} 2604] Fe 61 0.033} 2693 
These counts for the test and final control bulbs suggested so 
strongly that the number of cells is the same for bulbs of different 
sizes that attention was turned entirely to the investigation of 
this point. At first longitudinal sections were used, but these 
were soon abandoned for two reasons. First, it seemed desirable 
to be able to count the cells of just that portion of the bulbs 
corresponding to the part weighed; and second, the longitudinal 
sections presented so many irregularities that 1t was necessary 
to count many more sections to approximate the true average 
than in the case of the cross sections. Counts were made of all 
elements in the gray layer outside the mitral layer between the 
tip of the bulb and the point at the proximal end where the gray 
layer is first interrupted on the dorsal aspect of the bulb (see 
figs. 5, 6, 7). These counts consumed a vast amount of time 
and when completed seemed to disagree with the observations 
already made upon the longitudinal sections (table 2). 
A first glance at the table would indicate that the small bulb 
has fewer cells and would suggest that this difference in cell 
