THE BLOOD CELLS 



79 



stage is recognized as tlic ])remyelo('yte, of which three forms can 

 be distinguished on tlie hasis of cytoplasmic granulation. The 

 nuclei are spherical or reniform at first, but each type undergoes 

 further mitoses with further differential granulation of the cyto- 

 plasm and lobulation of the nucleus until neutrophil myelocytes, 

 4 



"a; 



8 \:^ 



Fig. 42. — Diagrammatic representation of the components of red bone-marrow. 

 1, fat cell; 2, hemocytoblast; 3, erythro blast; 4, normoblast; ,5, erythrocyte; 6, myelo- 

 cyte; 7, neutrophil; 8, eosinophil; 9, basophil; 10, megakaryocyte; A, reticular tissue; 

 B, cell of sinusoid wall; C, sinusoid. 



eosinophil myelocytes, and basophil myelocytes are formed. P^ach 

 of these types undergoes its own special development leading to the 

 formation of completely differentiated neutrophils, eosinophils, and 

 basophils which enter the circulating blood by way of the sinusoids. 

 Megakaryocytes. These giant cells are usually spherical in form 

 and are found extravascularly in the red marrow of mammals. 

 They also arise from hemocytoblasts by a series of transitional 

 forms. Xormally they remain in the marrow, where they are 



