BLOOD. 



Normal Percentage of Each Variety (Cabot). 

 Small lymphocytes ............ . ............. 20-30 per cent. 



Large " ........................... 4-8 



Polymorphonuclear neutrophiles ................ 62-70 " 



Eosinophiles ................................. 5-4 



" Mast cells" 



Description of the Different Varieties. The variety which is most 

 numerous, as may be seen from the above table, is the so-called 

 polynuclear or polymorphonuclear neutrophile. With Wright's 

 stain, the nucleus of this corpuscle takes an intense navy-blue color 

 and is sharply defined. The nucleus is irregular in outline and 

 may assume a great variety of forms. There may be two or more 

 nuclear masses united by finer bands of nuclear substance. The 

 cytoplasm contains fine granulations which take, with Wright's 

 stain, several different shades of pink. Where the simple eosin 

 and methylene-blue staining is employed, these granules take a 

 faint pink tinge. 



The lymphocytes, which, in point of number, come next to the 

 polynuclear neutrophile, vary considerably in size, from that of a 

 red blood corpuscle to several times the size of a red. The nucleus 

 is large, generally round, but may be oval or bean-shaped. There 

 is but a narrow rim of cytoplasm around the nucleus. The cyto- 

 plasm, with Wright's stain, takes a robin 's-egg-blue tint and the 

 nucleus stains a deep purple or purple-blue. 



Granules are, as a rule, absent. Forms are seen, however, in 

 which the cytoplasm contains from a few to a large number of 

 pinkish but more generally blue granules. 



The eosinophile is a large cell, resembling, in structure and 

 size, the polynuclear neutrophile. With Wright's stain, the nuclei 

 stain light blue or lilac, with an ill-defined intranuclear network. 

 The large spherical or oval granules take a brilliant red eosin 

 stain. The cytoplasm around the granules either takes no stain 

 whatever or a pale blue tinge. This type of leucocyte occurs nor- 

 mally in very small numbers, and a number of fields may be gone 

 over with the microscope before an eosinophile is found. 



[67] 



