230 NORMAL AND PATHOLOGICAL BLOOD 



mononuclears. Tiirck supposed them to appear in the circulation as 

 the result of bone-marrow irritation. 



4. Myeloblasts. These cells are found in myeloid leukaemia and 

 though often mistaken for lymphocytes or large mononuclears they are 

 of marrow origin. They are the lymphoid cells of the marrow and are 

 the parent cells of myelocytes. The nucleus stains more intensely 

 than that of the large mononuclear and the cytoplasm is more deeply 

 blue stained than that of the large lymphocyte. They also contain 

 three or four nucleoU. 



Pyronin methyl-green staining is best for demonstrating the nuclei. 



5. Pathological Large Lymphocytes. These are, as a rule, much 

 larger than normal large lymphocytes and show poorer staining of both 

 nucleus and cytoplasm. The nuclei often show the appearance of 

 division into two or more lobes, thus showing the characteristics of 

 Rieder cells. 



They may be confused with large mononuclears but are considered to be derived 

 from the germinal centers of various lymphoid tissues. They are found in leukaemic 

 and pseudo-leuksemic conditions. 



6. Megakaryocytes. These are the giant cells of the bone marrow 

 and are but rarely found in the blood. The nucleus is gnarled. 



BLOOD PLATELETS 



These are normally present in blood in the number of about 350,000 per cubic milli- 

 meter. They disintegrate very quickly after the blood is withdrawn. Wright has 

 demonstrated that they are pinched-off projections of giant cells of the bone marrow. 

 They consist only of protoplasm, no nuclear material. They do not contain haemo- 

 globin. In conditions where giant cells are less abundant, as in pernicious anaemia, 

 the blood platelets are less abundant. In myelogenous leukaemia they are very abun- 

 dant. They vary in size from 2 to 5/1 according as a larger or smaller pseudopod of a 

 giant cell has been broken off. Stained with Wright's stain, they are more purplish 

 than blue and show thread-like projections. They are often mistaken for the proto- 

 zoal causes of various diseases. Especially are they confused with malarial para- 

 sites when lying on a red cell. The blood plate has no brick-red chromatic material; 

 it is purplish rather than blue, and has no pigment grains. It is advisable to com- 

 pare these isolated blood plates with the larger or smaller aggregations scattered 

 about the smears. In this way their true character is apparent. In addition to 

 blood platelets, which in fresh blood can only be observed when a fixative is used, we 

 have other confusing bodies. 



The hamokonia of Muller are small, highly refractile bodies showing active 

 oscillatory movement. They are supposed to be cast-off granules of eosinophiles or 



