244 CAROLINE M. HOLT 
bulb. The number for X.s, whose weight was 0.040 gram, 
was 73,950. ‘To see whether there were any virtue in making 
so thorough a count of cross sections, the total number was 
computed from a recount of every 10th section, excepting at 
the most anterior end where every cell was counted in every 
section, until the sections showed a single layer of mitral cells. 
By this method the number obtained for X, was 64,775 cells, 
making a difference of only 0.4 per cent. For X, the count was 
73,324, which was 0.8 per cent smaller than the more exact 
count obtained by counting half the sections. These differences 
were so small as to make the more exhaustive count seem un- 
necessary. X, gave an almost complete series through the 
entire gray layer so the count was completed, giving for the entire 
bulb 80,114 cells. The count of the mitral cells in X; could not 
be completed as the series had been cut, unfortunately, with the 
idea of comparing only the parts of the bulbs whose weights we 
knew, and which, therefore, extended back but a short distance 
under the cerebrum. ‘The cells of these few sections were, how- 
ever, counted, giving a total of 71,914. 
The number of mitral cells in Gs was computed from absolute 
counts of anterior and posterior ends of the series and by count- 
ing every tenth section through the rest of the series. M,, M; 
and @; ran so evenly that here in the middle portion of each 
series, only every twentieth section was counted; on either side 
of this portion, every tenth section, and all cells of all sections 
at either end. 
With the sagittal sections, the task was more difficult and the 
results, I believe, less reliable for this reason: toward the sides 
of the bulbs, especially the median side, the sagittal series may 
give tangential sections of the mitral layer so that a single section 
may yield a count of 1500 cells whereas a section two or three 
removed on either side might have but 300 or so mitral cells. 
It can be easily seen that if the section to be counted, happened 
to fall in such a region, or entirely skipped such a region, the 
count would be considerably modified. Some of the bulbs 
gave no trouble of this kind while others were hard to count for 
this reason. G,; was an interesting example of the way this 
