BLOOD PLATELETS AND HEMOKONIA. l6l 



3. The Irritation Cell of Turck, or Plasma Cell. This cell has a 

 faintly-staining, eccentrically-placed nucleus, and a dark opaque blue, 

 frequently vacuolated, cytoplasm. They are usually recorded as large 

 mononuclears. 



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 withdrawn.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 pernicious 

 anaemia, the blood platelets are less abundant. In myelogenous 

 leukemia they are very abundant. 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-light 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 w r ith 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 hemokonia of 

 Muller are small, highly refractile bodies showing active oscillatory 

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

 or other leukocytes. Pinched off fragments of red cells may also 

 appear as possible protozoal bodies. 



LEUKOPENIA. 



This is a term used to designate a reduction in the normal number 

 of leukocytes. A leukocyte count of 5000 would represent a slight 

 leukopenia; one of 2000, a marked leukopenia. In the later stages of 

 typhoid, and in acute miliary tuberculosis, we expect a moderate 

 leukopenia. Chronic alcoholism and chronic arsenic poisoning cause 



