120 



NORMAL HISTOLOGY. 



closely applied to the bone that is being removed, and have in this 

 situation been called " osteoclasts." Fifth, basophilic cells, or plasma- 

 cells, the cytoplasm of which contains granules having an affinity 



FIG. 103. 



Cells from bone-marrow : a, small leucocyte from circulating blood, with highly chromatic 

 nucleus and slight amount of cytoplasm, a " lymphocyte " probably derived from a lymph- 

 node ; b, b, myelocytes, larger than a, with vesicular nuclei ; c, c, c, erythroblasts, with 

 nuclei in karyokinesis ; c', mature red corpuscle (erythrocyte) ; d, acidophile (eosinophile) 

 leucocyte. The basophilic leucocytes, or plasma cells, resemble this, but have smaller 

 and less abundant granules of different chemical nature ; e, giant-cell (myeloplax) with 

 three nuclei ; a, b, c, and d, from the marrow of the fowl (Bizzozero), the red corpuscles of 

 which are oval and nucleated, c' ; e, from the marrow of the guinea-pig. (Schiifer.) 



for " basic " anilin-dyes, such as dahlia. These cells are relatively 

 large, and possess vesicular and frequently polymorphic nuclei. 

 Aside from these cells, which may be regarded as forming a part 

 of the marrow, it contains red blood-corpuscles and leucocytes, 

 either formed within the marrow or brought to it by the circulating 

 blood. 



The functions of the various cells in bone-marrow have not been 

 finally determined, but it is certain that the erythroblasts, by their 

 multiplication and transformation, maintain the supply of red cor- 

 puscles circulating in the blood. 



The arteries supplied to the marrow divide freely and open into 

 small capillaries, which appear subsequently to dilate, and either to 

 blend with the endothelial elements of the reticular tissue or to 

 become pervious through a separation of the cells forming their 

 walls. In either case the blood passes into the meshes of the retic- 

 ular tissue, where it slowly circulates among the constituents of the 

 marrow. It then passes into venous radicles devoid of valves, and 

 is thence conveyed from the bone. In some animals e. g., birds 

 the production of red corpuscles appears to be confined to the venous 



