WHITE BLOOD CORPUSCLES 75 



subject to constant variations from physiological causes, e. g., 

 digestion, absorption, etc. 



Varieties of White Blood Corpuscles. After fixation and stain- 

 ing the nucleus, as well as the cytoplasmic granules, is found to 

 present characteristic differences in the several varieties of white 

 blood corpuscle. The nuclei of the non-granular cells mono- 

 nuclear leucocytes are spheroidal in shape, have a fairly distinct 

 nuclear membrane, and possess a varying amount of irregularly 

 distributed chromatin. The size of the nuclei of these cells is 

 also variable, and upon these differences two cell types are recog- 

 nized, the large and the small mononuclear. 



The small mononuclear leucocytes lymphocytes possess a 

 highly chromatic and therefore deeply staining nucleus of small 

 size which occupies nearly the entire cell, the encircling rim of 

 cytoplasm being extremely narrow and at times scarcely demon- 

 strable. The large mononuclear cells " spleenocytes " of Virchow 

 possess a wider cytoplasmic rim and a large nucleus with a dis- 

 tinct nuclear wall ; the nucleus in contradistinction to that of the 

 lymphocyte is deficient in chromatin, and therefore is- but lightly 

 stained with nuclear (basic) dyes. 



The cytoplasm of the mononuclear cells under moderate mag- 

 nification presents a hyaline structureless appearance, but with 

 higher magnifying power a delicate reticulum and at times, 

 especially in the large mononuclear forms, very fine neutrophile 

 granules can be demonstrated. 



The nucleus of the mononuclear forms, but much more fre- 

 quently that of the larger variety only, occasionally deviates from 

 its typical spheroidal form, being notched, indented, or even of 

 almost a horseshoe shape. In this latter form these nuclei some- 

 what resemble those of the polynuclear cells to be described, yet 

 they are readily distinguished therefrom by their characteristic 

 deficiency in nuclear chromatin and cytoplasmic granules. 



The finely granular white blood cetts polynuclear leucocytes 

 after fixation and staining, present a highly chromatic, deeply 

 basophilic nucleus which varies greatly in form. Thus it may be 

 indented, horseshoe-shaped, S-shaped, elongated and twisted upon 

 itself, or separated into distinct lobes which are connected together 

 by means of fine chromatic filaments. It is thus characteristically 

 polymorphous, but in all its varying forms it is readily distinguish- 

 able from the mononuclear types by its extreme depth of stain, its 

 intense cJiromatophilia. 



