TRANSITIONAL LEUKOCYTE. 



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normal human blood are divided into five classes, namely : 

 small mononuclear, large mononuclear, transitional, poly- 

 nuclear (or polymorphonuclear), and eosinophile. 



FIG. 41. 



Leukocytes of human blood, a, small mononuclear leukocyte, stained; 6, large 

 mononuclear leukocyte, stained; c, transitional leukocyte, stained; d, e, , poly- 

 morphonuclear or ne'utrophile leukocyte, living appearance, showing distinc- 

 tion of hyaloplasm and granuloplasm and amoeboid movement ; /, polymorpho- 

 nuclear leukocyte, in fresh state, treated with acetic acid ; g, h, i, polymorpho- 

 nuclear leukocyte, stained; k, eosinophile leukocyte, living appearance; I, 

 eosinophile leukocyte, stained. 



The small mononuclear leukocyte, or small lymphocyte, is 

 about 6 to 8 micromillimetres in diameter (about the same as 

 red corpuscles), and has a single large spherical, deeply stain- 

 ing nucleus, surrounded by a small amount of faintly-stain- 

 ing non-granular protoplasm, which forms a small cell-body. 

 Morphologically and genetically it is similar to or identical 

 with lymph-corpuscles. 



The large mononuclear leukocyte, or large lymphocyte, the 

 largest corpuscle of normal blood, is 12 to 15 micromillimetres 

 in diameter, contains a single, very large, rounded nucleus 

 that does not stain very deeply, and has a large body of non- 

 granular, faintly staining protoplasm. Sometimes no sharp 

 line can be drawn between this and the preceding class, all 

 intermediate gradations of size and coloration being present. 



The transitional leukocyte is like the large mononuclear 



