192 BLOOD AND BLOOD-FORMING ORGANS. 



They vary in size from 5 ^ to 7. 5 // and possess a relatively large 

 nucleus, the chromatin of which is in the form of relatively large 

 granules, which stain rather deeply. The nucleus is surrounded by 

 a narrow zone of protoplasm, often seen clearly only to one side of 

 the cell in the form of a crescent. It does not stain readily in acid 

 dyes. 



The leucocytes vary in size from 7 p. to 10 fJt. The mononuclear 

 leucocytes, constituting about 2^ to 4^ of the white blood-cells, 

 have a nearly round or oval nucleus, which usually does not stain 

 very deeply, and which is relatively smaller than that of the lympho- 

 cytes. The transitional leucocytes, forming also about 2% to 

 4^ of the white blood-cells, are developed from the mononuclear 

 variety and represent transitional stages in the development of 

 mononuclear leucocytes to those with polymorphous nuclei. The 

 nucleus in the transitional form is similar in size and structure to that 

 of the mononuclear variety, but of a more or less pronounced horse- 

 shoe-shape. The leucocytes with polymorphous nuclei, developed 

 from the transitional forms, are very numerous in the blood, form- 

 ing about 70 % of the entire number of white blood-cells. They 

 are also the cells which show the most active ameboid movement 

 when examined on the warm stage. They possess variously lobu- 

 lated nuclei, the several nuclear masses often being united by del- 

 icate threads of nuclear substance. A leucocyte with a poly- 

 morphous nucleus becomes a polynuclear cell in case the bridges 

 of nuclear substance uniting the several lobules of the nucleus break 

 through. In the protoplasm of the transitional leucocytes, the 

 polymorphonuclear, and the polynuclear forms are found fine and 

 coarse granules. Our knowledge of these granules has, however, 



a e /3 y 6 



Fig. 158. Ehrlich's leucocytic granules; X J 8oo (from preparations of H. F. 

 Miiller) : a, Acidophile or eosinophile granules, relatively large and regularly distributed ; 

 e, neutrophile granules ; (3, amphophile granules, few in number and irregularly dis- 

 tributed ; y, mast cells with granules of various sizes ; 6, basophile granules, (a, 6, and 

 e, From the normal blood ; y, from human leukemic blood ; (3, from the blood of 

 guinea-pig.) 



been greatly extended since Ehrlich has shown that the granules of 

 leucocytes show specific reactions toward certain anilin stains, or 

 combinations of such stains. He divides the granules of the leuco- 

 cytes into five classes which he terms respectively -, /9-, 8-, Y-, and e- 

 granules. In human blood are found the a-granules, which show an 

 affinity for acid-anilin stains, are therefore known as acidophile gran- 



