BLOOD PLATELETS I 95 



mononuclears. Turck 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. 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 nucleoli. 



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 lym- 

 phoid tissues. They are found in leukaemic and pseudo-leukaemic 

 conditions. 



BLOOD PLATELETS. 



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

 millimeter. They disintegrate very quickly after the blood is withdrawn.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 haemoglobin. In conditions where giant cells are less abundant, as in per- 

 nicious anaemia, the blood platelets are less abundant. In myelogenous leukaemia 

 they are very abundant. They vary in size from 2 to 5/f 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 protozoal causes of various diseases. Especially are they confused 

 with malarial parasites 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 compare these isolated blood plates with the larger or smaller ag- 

 gregations scattered about the smears. In this way their true character is apparent. 

 In addition to blood platelets, which in fres.h blood can only be observed when a 

 fixative is used, we have other confusing bodies. 



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

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

 or other leukocytes, or possibly derived from nuclei. As this blood dust or haemo- 

 konia is found in a marked degree in lipaemia it may be that the particles are fat. 

 It is interesting that this lipaemia is absent after the taking of large quantities of 

 fat in cases with serious pancreatic trouble. The serum of a normal individual is 

 rather turbid after slight indulgence in butter. Pinched-off fragments of red cells 

 may also appear as possible protozoal bodies. 



