258 TEXT-BOOK OF PHYSIOLOGY 



arrests the movements. Induced electric currents also cause contraction 

 and death of the cell. Moisture and oxygen are necessary to their activity. 

 From their similarity to lower organisms the white corpuscles may be re- 

 garded as independent organisms living in the animal fluids, just as the 

 amoeba lives in its natural liquid medium. 



Varieties of Leukocytes. A detailed study of the blood with the aid 

 of the triacid staining fluid of Ehrlich or any of the various eosin and methy- 

 lene-blue stains, reveals the presence of five distinct varieties of leukocytes 

 and transitional forms which may be classified as follows: 



1. Small lymphocytes, so called from their resemblance to the corpuscles 



of the lymph-glands, consisting of a deeply staining and relatively 

 large round nucleus, encircled by. a narrow rim of cytoplasm. Found 

 in from 20 to 25 per cent, of all leukocytes. They vary in size from 

 0.004 to 0.007 mm - 



2. Large lymphocytes or hyaline cells, which are believed by some to represent 



the preceding type at a later stage of development, by others to have an 

 independent origin, are distinguished by a round or ovoid nucleus 

 staining faintly and surrounded by a relatively larger layer of cytoplasm 

 than is seen in the small lymphocyte. The large lymphocyte is present 

 to the extent of from 4 to 8 per cent. Transitional forms, usually pre- 



A B .c 



FIG. 108. LEUKOCYTES AS SEEN IN A SECTION OF HUMAN TISSUE PRESERVED WITH 

 ZENKER'S FLUID. A, Lymphocyte; B, large mononuclear lymphocyte; C, three polymor- 

 phonuclear leukocytes. (Lewi? and Stohr.) 



sent from i to 2 per cent, are very much like the large lymphocyte in 

 appearance and size, with the exception, however, that they possess a 

 cresentic or indented nucleus and have a somewhat greater affinity for 

 basic dyes. They are usually counted with the large lymphocytes. 

 Both varieties of lymphocytes are characterized by a cytoplasm 

 which is devoid of granules. Rarely, basophilic granules may be 

 present. 



3. Polymorphonuclear leukocytes. The nucleus of this cell is irregular 



and assumes a great variety of shapes in different cells, a feature which 

 has suggested the name given to the cell. The perinuclear cystoplasm 

 contains a large number of fine granules which are decidedly acid- 

 ophilic in their staining reaction. They make up about 60 to 70 per 

 cent, of the whole number of the white blood-cells. They vary in 

 size from 0.007 to o.oio of a mm. (Fig. 108). 



4. Eosinophile cells. The nucleus resembles in many respects that of the 



preceding variety; it is, however, less apt to stain so deeply. It is also 

 very irregular in shape and many cells possess several apparently dis- 

 tinct nuclei. The cytoplasm is ill-defined but its presence is easily 

 revealed through the large, intensely acidophilic granules which it 

 possesses. 



It is present to the extent of 0.5 to 2 per cent. 



