122 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



Histologically, we find in marrow all the con- 

 stituents of blood and connective-tissue elements, 

 fibers and cells. In addition, the following are some 

 of the more characteristic cells of this tissue : 



i . Hematoblasts or Nucleated Red Blood-corpuscles. 

 These cells contain hemaglobin and a small round 

 nucleus that stains heavily with hematoxylin. They 

 are supposed to be the chief source of the red blood- 

 corpuscle, in which case the nucleus must disappear 

 either by disintegration or extrusion. 



2. Marrow Cells or Myelocytes. These are large 

 cells with a rather large nucleus that stains lightly. 



3. Eosinophiles. These are destined to become 

 the eosinophile of the blood. 



4. Giant Cells (myeloplaxes or osteoclasts) . 

 These are very large poly nucleated cells, having 

 from ten to twenty nuclei. Cells of this class are 

 not numerous, but extremely large (30 to 100 /w). 



They may be found in the fetal 

 liver or spleen, and are very char- 

 acteristic of developing bone. They 

 present a finely granular proto- 

 plasm without any cell wall. The 

 clei ar e bunched about 



tais from blood- the center of the cell, and in this 



stains of man. - -._. f - 



respect they differ from the giant 

 cells found in tuberculosis foci, in which the nuclei 

 are found near the periphery. They multiply by 

 mitosis, and primarily are supposed to be derived 

 from leucocytes by endogenous division of their 

 nuclei. These remarkable cells have usually been re- 

 garded as the active agents in bone absorption, but 

 recently Wright has suggested that blood platelets 



