25 
or Red Disks of the Mammiferous Anmals. 
in the relative exactness of the instrument I arn disposed from 
long experience to put much confidence, which is of the 
greatest importance where the results are to be obtained 
chiefly by comparisons. 
The corpuscles were examined thinly spread on glass and 
quickly dried, also floating in their own serum, and diluted 
when necessary with weak saline solutions, or sugar and water, 
or with urine. The objection to these substances is, that they 
all more or less alter the figure of the globules, generally ren- 
dering many of them cup-shaped and diminishing their size 
slightly. Indeed, the disks kept in their own serum often ap- 
pear a little smaller in a very short time after they have been 
removed from the vessels, as if they possessed some degree of 
contractility. It might be supposed that the particles rapidly 
dried on glass would shrink a little; but this is not the case, 
for they retain a remarkably clear and regular outline, and 
are commonly, to a small extent, larger than those of the same 
blood exposed to the air in their own fluid. 
In some instances there was certainly a slight enlargement 
in the dried corpuscles, as compared with those seen in their 
own serum immediately after they were taken from the ani- 
mal. In the greater number of trials, however, the sizes of 
the wet and dry disks corresponded accurately. In most cases 
the measurements were repeated by Mr. Siddall, an experi- 
enced micrographer, with another instrument by Ross, so as to 
avoid as much as possible accidental inaccuracies. The mea- 
surements are always expressed in fractions oFan English inch. 
As the corpuscles are very liable to change in size and form 
from very trivial causes, the extreme measurements in no case 
include those large or small particles which occur but spa- 
ringly, and which, perhaps, are not identical with the common 
red disks. Neither the large white globules nor the granu- 
lated particles are estimated, because, independently of their 
spherical shape, the former are almost uniformly larger and 
the latter smaller than the blood disks. As noticed by Hew- 
son, the common corpuscles become mulberry-shaped when, 
from incipient putrefaction, their colouring matter begins to 
dissolve in the serum. But 1 have observed the granulated 
particles in great numbers, both in their serum and in the 
dry state*, in blood examined immediately after it was ob- 
tained from the veins of various animals, particularly young 
kittens. The nature of these particles is worthy of further 
and special inquiry. They are to be found plentifully during 
* I gave Mr. Owen specimens of these granules in September last, men- 
tioning this Fact to him, as he considered the granulated appearance to be 
the effect merely of drying. 
