100 BLOOD AND LYMPH. 



form, except that its single large nucleus, instead of being 

 spherical, is more or less indented at one side, tending toward 

 a horseshoe shape ; the body-protoplasm also sometimes con- 

 tains a few fine granules. In the shape of its nucleus it is an 

 intermediate form between the large mononuclear and the 

 polymorphonuclear variety. It is, however, closely related to 

 the former, all gradations being present so that a sharp line 

 can scarcely be drawn between the large mononuclear and the 

 transitional ; on the contrary (especially with respect to the 

 absence of granules), there is a sharp gap between the transi- 

 tional and polymorphonuclear varieties not filled by inter- 

 mediate gradations. Transitional leukocytes are often to 

 be regarded simply as a variety of the large mononuclear 

 group. 



The polymorphonuclear, polynuclear , or neutrophile leukocyte 

 is about 10 micromillimetres in diameter, has a large cell- 

 body of active protoplasm, containing large numbers of fine 

 neutrophile (s) granules, and a very variable, irregularly 

 shaped, deeply staining nucleus. Often, especially after the 

 action of reagents, the nucleus appears to consist of about 

 three separate, rounded nuclei ; whence until recently the term 

 polynuclear was the prevalent designation of this leukocyte. 

 At present the opinion is gaining ground that in most cases, 

 instead of three separate nuclei, the living corpuscle contains 

 one long twisted and irregular nucleus, so that the name poly- 

 morphonuclear is now considerably used. This is the most 

 active and much the most abundant variety of leukocyte in 

 the blood, and is also the form found in pus. It exhibits 

 active amoeboid movements, and the distinction of hyaloplasm 

 and granuloplasm in its body can often be made out. 



The eosinophile (or oxyphile) leukocyte is about 10 /2 in 

 diameter; its nucleus, except that it stains less deeply, is 

 similar to that of the polymorphonuclear variety, being poly- 

 morphous and irregular, or perhaps multiple ; the body-proto- 

 plasm is crowded with conspicuous coarse spherical oxyphile 

 or eosinophile (a) granules. In microscopical specimens the 

 granules surround but do not overlie the nuclei, leaving the 

 latter as clear spaces. This leukocyte has a striking appear- 

 easily recognized, both in the living and stained 

 fe^the least common variety in the blood. Its 



i :_. 

 BRA 



