BLOOD PLATES 37 



sionally one or more compact, rounded, deeply staining (deep 

 purple with Wright's stain) bodies about the size or somewhat 

 larger than a mast cell granule. These bodies are probably a 

 result of degeneration. The thrombocytes show a marked tend- 

 ency to collect in clumps. In fresh blood and in the less thinly 

 spread parts of films, they collect in masses in which it is difficult 

 to distinguish the outline of individual cells. This indistinctness 

 of cell outline and structure shows another property of these cells, 

 that is their vulnerability. They change quickly when taken 

 from the blood vessels, passing through a characteristic series 

 of changes. Both cell body and nucleus become less distinct, the 

 cell body losing its structure first. Finally both become structure- 

 less, appearing in stained preparations merely as a diffusely stained 

 mass, the nucleus being distinguishable by having a slight by 

 deeper stain. 



Hayem and Goodall call these cells hematoblasts. Their func- 

 tion and properties, however, show them to be similar to the 

 blood plates in mammals. As the thrombocytes are nucleated 

 they cannot be homologous with blood plates. Wright considers 

 them homologous with the megakaryocytes from which the blood 

 plates are derived. For his opinion he gives two reasons, first 

 that the forerunners of the megakaryocytes are circulating cells, 

 as may be seen in embryo guinea pigs, and second that in certain 

 Amphibia the thrombocytes regularly lose their cytoplasm by 

 a pinching off process similar to that which takes place in the for- 

 mation of blood plates. 



Blood dust (hemokonia). These are minute spheroidal or 

 spindle-shaped bodies of one-fourth to one micron in diameter 

 found in the blood. They were first described by Bizzozero and 

 later by Miiller. These bodies are insoluble in acetic acid, alcohol 

 and ether and are not blackened by osmic acid. Stokes and Wege- 

 farth found them to vary in size in different animals according to 

 the size of the granules of leucocytes. They regard them as 

 extruded granules of polymorphs and eosinophiles. These 

 bodies have not been shown to have any special clinical sig- 

 nificance. 



