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 Miiller ; 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 t Donne to be the spleen. 



102 



