226 NORMAL AND PATHOLOGICAL BLOOD 



There is not that sharp distinction between nucleus and cytoplasm that exists in 

 the lymphocytes. The cytoplasm of the large mononuclear gives the impression of 

 opacity, as if it were frosted glass instead of clear glass. The neutrophile mottling 

 which begins to appear causes a disappearance of the pure blue character of the cyto- 

 plasm of the lymphocyte. It is principally by the washed-out staining of the nucleus 

 and the opaque lilac of the cytoplasm that we differentiate them from the lympho- 

 cytes. They greatly resemble Turck's irritation forms or plasma cells and may be 

 confused with myelocytes. 



3. Transitionals. These appear as but a later stage in the decay 

 of the large mononuclears; the nucleus is more indented, frequently 

 horseshoe-shaped, and has a washed-out violet shade of less intensity 

 than that of the large mononuclears. These are the cells so often dis- 

 rupted in smears. The old view that the transitional was the pre- 

 cursor of the polymorphonuclear has few advocates at the present 

 time. 



While it may be convenient to consider hyaline cells as representing different stages 

 in development, yet from a standpoint of immunity this is untenable. The large 

 mononuclears and transitionals are the cells in which we find certain animal cells 

 and pigment phagocytized, as is the case in malaria. These cells are the macro - 

 phages of Metchnikoff and are probably derived from the bone marrow. 



In the tropics one of the most important points in a differential 

 count is the matter of an increase in the large mononuclears and 

 transitionals, both of which seem to respond to the same stimulus, 

 which is most commonly malaria but may also be from other protozoal 

 infections. 



From a practical standpoint I always group them together and as a matter of fact 

 it is difficult to separate a large mononuclear showing considerable irregularity of 

 nucleus from a transitional with less marked nuclear indentation. 



The lymphocytes take origin from the lymphoid tissue, and very 

 probably the large lymphocyte is a younger, more immature cell than 

 the small lymphocyte. 



Ehrlich and Naegeli regard the large mononuclears as of myeloid origin while 

 Pappenheim considers them to belong to the group of lymphocytes. 



A normal percentage of large mononuclears and transitionals com- 

 bined should not exceed about 4%. 



GRANULE CONTAINING LEUKOCYTES 



In addition to the series of leukocytes just considered we have present 

 normally in the blood three types of granular cells distinguished 

 according to the staining affinity of their granules. These are: 



