MICROSCOPIC DRAWING AND ENGRAVING. 
of the camel species. It appears, from some recent observations 
of Dr. Mandl, that the blood of this species presents an anomalous 
exception, the red corpuscles being elliptical in their form, but 
still flat and concave at their sides. 
In comparing the red corpuscles of the blood of different species 
of mammalia, or suckling animals, one with another, they are 
found to vary in their diameters, being greater or less in different 
species, but the variation in each species being confined within 
narrow limits, as in man. 
The corpuscles of the blood of birds, fishes, and reptiles, are all 
like those of the exceptional case of the camel, oval discs of 
various magnitudes, somewhat concave in their centres, like the 
blood of mammalia. 
77. The discovery of the white globules is entirely due to recent 
observers, and particularly to Professor Muller, Dr. Mandl, and 
Dr. Donne. 
The white globules have nothing in common with the red 
corpuscles, either as to colour, form, or composition. Unlike the 
latter, they are spherical, their contour is slightly fringed, and 
not well defined like that of the red corpuscles; their surface is 
granulated, and their diameter is a little greater, varying from 
the 2500th to the 3000th of an inch. They appear to consist of 
a thin vesicle, or envelope, the interior of which is filled with 
solid granulated matter, consisting usually of three or four grains, 
while the red corpuscles are filled with an homogeneous and 
semi-fluid matter in the case of mammalia, and a single solid 
kernel in the case of other vertebrated animals. 
The white globules also have chemical properties totally 
different from those of the red corpuscles. 
78. In fine, the third class of solid particles which float in the 
blood cannot be properly denominated globules, being only very 
minute granulations, which are continually supplied by the chyle 
to the sanguineous fluid; they appear in the microscope as minute 
roundish grains, isolated, or irregularly agglomerated, and having 
a diameter not exceeding the 8000th of an inch: they have, 
however, a physiological importance of the first order, since they 
are the primary elements of the blood, and therefore of all the 
other organised parts of the body. 
79. It appears to follow from the observations, researches, 
experiments, and reasoning 'of Dr. Donne, that these granular 
particles form themselves into the white globules by grouping 
themselves together, and investing themselves with an albuminous 
envelope. By a subsequent process, the white globules are con¬ 
verted gradually into the red corpuscles, the place where this 
change is produced being supposed by Dr. Donne to be the spleen. 
102 
