SECTION I 

 THE WHITE BLOOD-CORPUSCLES 



AMCEBOID cells are a constant constituent of the coelomic fluid in 

 all classes of animals. Even in the lower metazoa, where there is not 

 yet a body cavity, wandering mesoderm cells are present which 

 apparently discharge functions analogous in all respects to those of 

 the white blood-corpuscles of mammals. On carefully examining a 

 specimen of human blood, either fresh or in the form of a thin stained 

 film, several varieties of these cells are seen to be present. In a fresh 

 specimen we can distinguish the following varieties : 



(a) A cell with a lobed nucleus and finely granular protoplasm ; 



FIG. 355. Various forms of leucocytes. 



a, eosinophile corpuscle ; b, ordinary polynuclear leucocyte (' neutrophile ' ) ; 

 c, hyaline corpuscle ; d, lymphocyte. 



(b) A small cell consisting almost entirely of a nucleus surrounded 

 by a thin layer of protoplasm ; 



(c) A cell with a single nucleus and clear hyaline protoplasm ; 



(d) A cell with a lobed or reniform nucleus, the cytoplasm being 

 beset with large coarsely refracting granules. 



These four types are known as the finely granular or polymorpho- 

 nuclear cell, the lymphocyte, the hyaline corpuscle, and the coarsely 

 granular corpuscle. 



The differentiation of the various types of leucocytes is more 

 easily made if recourse be had to staining with mixtures of aniline 

 dyes. This method was introduced by Ehrlich, who classified 

 leucocytes according to the staining characters of their granules, 

 dividing the latter into : 



(a) Those staining with acid dyes, such as eosin acidophile or 

 eosinophile granulation ; 



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