BONE-MARROW 



221 



also present, but indistinguishable from the lymphocytes and hemogenic 

 polykaryocytes respectively unless specially stained. 



A description of the cells in their order of hemogenic cytomorphosis 

 follows : 



1. Myeloblast (Premyelocyte; HemoUast, Mesameboid Cell; Prim- 

 itive Blood Cell; 'Lymphocyte'); This is the parent blood-cell of bone- 



FIG. 234. TYPES OF CELLS FROM A SMEAR PREPARATION OF THE MARROW OF A 



HUMAN RIB. 



1, red blood corpuscles; 2, nucleated red blood cells, erythroblasts; 3, small lympho- 

 cytes; 4, large mononuclear cells with neutrophil granules; 5, polynuclear neutro- 

 phil; 6, eosinophil cells; 7, a basophil cell. Eosin and methylene blue. Nocht's 

 stain. X 1200. 



marrow. It produces by proliferation and slight differentiation the more 

 direct ancestors of both the white (leukoblast) and red (megaloblast- 

 erythroblast) cells. Mother- and daughter-cells are similar in their 

 relatively large granular nuclei, well developed cell-body, ameboid capac- 

 ity, and proliferative activity. The cytoplasm of the myeloblast is homo- 

 geneous or very finely granular and slightly basophilic; likewise the 

 leukoblast. The megaloblast may be distinguished by its slightly oxyphil 

 character due to the presence of a small amount of hemoglobin. 



