DESCRIPTION OF PLATES. 161 
corpuscles in a given quantity of the fluid, by 
means of a hexemacetometer. 
After a considerable reduction of the number of 
red corpuscles as the result of hemorrhage, the 
usual proportion is often regained in an aston- 
ishingly short period. This fact shows that nature 
has provided liberally for their continued supply, 
to make up for deficiencies resulting from sudden 
loss, or from the disintegration which is no doubt 
constantly taking place in the circulation. 
Much difference of opinion has existed among 
physiologists as to the mode of origin of these cor- 
puscles; but it is now pretty well settled that a 
considerable proportion, at least, take origin from 
the colorless blood-corpuscles, about to be described. 
These colorless corpuscles are found in the blood 
in considerably less numbers than the red, and the 
relative proportion fluctuates greatly at different 
times. Thus, after a prolonged fast, they may be 
reduced to the proportion of one in a thousand; 
while after a hearty meal, this proportion may be 
increased to one in three or four hundred. Their 
relative proportion is also greatly increased in cer- 
tain diseased conditions. 
One or more white corpuscles are to be seen in 
each of the figures (Plates V. and VI.); and it will 
be noticed that in the photo-micrographs of the 
blood of yellow-fever patients, they contain certain 
highly refractive granules not seen in the blood 
from healthy animals (Plate V.). These granules 
are believed to be fat, either developed in the pro- 
toplasm of the corpuscles, or picked up from the 
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