CHAP. L] BLOOD. 47 



thus acting as "phagocytes/' and In this way, or otherwise, by 

 exerting some influence on the bacteria or the products of their 

 activity, modify the course of the disease of which the bacteria are 

 the essential cause. 



If the white corpuscles are thus engaged during their life 

 in carrying on important labours, we may expect them to differ 

 in appearance according to their condition as determined by their 

 work. On the other hand, we may suppose that there are distinct 

 kinds of white corpuscles, having different functions and possibly 

 different origins and histories. 



We may in human blood distinguish the following forms of 

 white corpuscles. The most common form of corpuscle is one, the 

 cell substance of which is finely or rather obscurely granular, that 

 is to say the granules are both small and not sharply defined by 

 difference in refractive power from the ground substance (Fig. 



C 



A' 



FIG. 1. DIFFERENT FORMS OF WHITE CORPUSCLES FROM HUMAN BLOOD. 

 (Magnified one thousand diameters.) 



A. Ordinary, finely or obscurely granular corpuscle, with irregularly shaped 

 nucleus. A'. The sam.e stained to shew nuclear network. B. Hyaline corpuscle 

 with spherical or oval nucleus. C. Immature corpuscle with scanty cell substance. 



D. Large corpuscle with conspicuous coarse, discrete granules staining very readily 

 with eosine : eosinophile cell. D'. The same stained to shew nuclear network. 



E. Corpuscle with discrete granules, not staining readily with eosine, but staining 

 readily with basic dyes such as methyl-blue. 



1, A). The nucleus of this form of corpuscle is irregular in shape, 

 being lobed or even composed of two, three or more parts united 

 by narrow threads. 



Less common than the above is a corpuscle, Fig. 1, B, the cell- 

 substance of which as a rule appears almost or even quite hyaline 

 and the nucleus of which is spherical, and shews very distinctly, 

 when appropriately stained, a 'nuclear network,' that is to say, 

 appears to consist of a network of stained threads, ' chromatin' 

 threads, and of an unstained or less deeply-stained material filling 

 up the meshes of the network. Such a nuclear network is also 

 present in the obscurely granular cell just spoken of, but appears 

 not to be seen so readily and has been overlooked. 



Both these cells exhibit amreboid movements and both are 

 able, after the fashion of an amoeba, to ingest solid matters from 



