THE BLOOD. 255 



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 neutrophiles. 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 neutrophilic or 

 faintly acidophilic 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. 



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. 



5. Basophile cells, the nucleus of which is round or slightly irregular. The 



granules, which may be large or small, are basophilic and stain more 

 deeply than the nucleus, though they have the same color. It is rare 

 for this cell to be present above 0.5 per cent, of all leukocytes. 



In abnormal states of the blood other forms of leukocytes are fre- 

 quently present, e.g., myelocytes, leukoblasts, myeloplaxes, etc., the 

 significance of which is not always apparent. 



Origin of the White Corpuscles. Of the various theories advanced to 

 explain the origin of leukocytes, that formulated by Ehrlich has found the 

 most credence. According to this theory the leukocytes may genetically be 

 classed into two groups. In the first group are the large and small lympho- 

 cytes which take their origin entirely from the lymph-adenoid tissues of the 

 body, e.g., the lymph-glands, solitary and agminated follicles of the intes- 

 tines, etc. As the lymph flows through these structures the lymph-corpus- 

 cles, as the future lymphocytes of the blood are called in these situations, are 

 washed out and carried by way of the lymph-stream into the general 

 circulation. 



In the second group are the transitional forms, the polymorphonuclear, 

 eosinophile and basophile leukocytes which originate from the bone-marrow 

 only. The immediate ancestors of these cells are known as myelocytes and 

 are normally found in the red bone-marrow. These cells, through transi- 

 tional stages, assume the characteristics of the leukocytes just mentioned and 

 pass directly into the capillaries of the marrow whence they are distributed 

 throughout the body. 



Several attempts have been made by different investigators to trace all 

 varieties of leukocytes to a common mother cell. While this is believed to 

 take place during embryonal life, the proofs of such an origin of leukocytes in 

 the normal adult are insufficient and unconvincing. 



After an unknown period of life the leukocytes undergo dissolution and 

 disappear. 



