434 



OF NUTRITION. 



no colour, and which seem to have a function altogether different ; these are 

 known as the white or colourless corpuscles. Their existence has long been 

 recognized in the blood of the lower Vertebrata, where, from being much 

 smaller than the red corpuscles, they could be readily distinguished. But it 

 is only of late, chiefly through the researches of Gulliver, Addison,* and 

 others, that they have been recognized in the blood of Man and other Mam- 

 malia; their size being nearly the same with that of the red corpuscles; and 

 the general appearance of the two (owing to the circular form of the latter, 

 and the absence of a proper nucleus,) being less distinct. It is remarkable 

 that, notwithstanding the great variations in the size of the red corpuscles in 

 the different classes of Vertebrata, the dimensions of the colourless corpuscles 

 are extremely constant throughout; their diameter seldom being much greater 

 or less than l-3000th of an inch. This has been observed even in those ani- 

 mals, the Musk-Deer, and the Proteus, which present the widest departure 

 from the general standard in the size of their red corpuscles ; so that the 

 colourless corpuscle is as much as four times the diameter of the red in one 

 instance; whilst it is not one-eighth of the long diameter of the red in the 

 other. Hence it would seem very improbable that the red can ever be con- 

 verted into the white, or the white into the red. The aspect of the two, under 

 the Microscope, is very different. Instead of presenting a distinct central 

 nucleus, like the red corpuscles of the Oviparous Vertebrata, or being en- 

 tirely destitute of granular contents, as are those of Mammalia when unaffected 

 by reagents, the colourless corpuscles are studded with minute granules, 

 which may be occasionally seen in active motion within them, and which are 

 discharged when the corpuscles are .treated with liquor potassse. They possess, 

 moreover, a higher refracting power than the red corpuscles; and are further 



distinguished from them by their greater 

 firmness, and by the absence of any dis- 

 position to adhere to each other ; so that, 

 when a drop of recent blood is placed 

 between two strips of glass, and these 

 are gently moved over one anoher, the 

 white corpuscles may be at once recog- 

 nized by their solitariness, in the midst 

 of rows and irregular masses formed by 

 the aggregation of the red. These white 

 corpuscles of the blood correspond so 

 closely, in all their characters, with the 

 Lymph-corpuscles, that it is difficult to 

 regard them as otherwise than identical ; 

 and, as already pointed out ( 566), the 

 corpuscles of the Chyle appear to be of 

 "the same character, though less perfectly 

 formed. The colourless corpuscles may 

 be readily distinguished in the circulat- 

 ing Blood, in the capillaries of the Frog's 

 foot ; and it is then observable, that they 

 occupy the exterior of the current, where 

 the motion of the fluid is slow, whilst the 

 red corpuscles move rapidly through the 

 centre of the tube. The colourless cor- 

 puscles, indeed, often show a disposition 

 to adhere to the walls of the vessels ; which is manifestly increased on the 



A small venous trunk a, from the web of the 

 Frog's loot, magnified 350 diameters; b. b, cells of 

 pavement-epithelium, containing nuclei. In the 

 space between the current of oval blood-corpus- 

 cles and the walls of the vessels, the round, 

 transparent, white corpuscles are seen. (After 

 Wagner.) 



* Transactions of the Provincial Medical Association, 1842 and 1843. 



