220 



BLOOD 



BONE-MARROW 



The red variety of bone-marrow, found in the flat bones generally 

 and in the epiphyses of long bones, functions as the sole hemopoietic or- 

 gan of later fetal and adult life. According to certain authorities it is 

 assisted in this function to some extent by the spleen. Besides a hemo- 

 poietic function, red bone-marrow possesses also the capacity of de- 



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FIG. 233. FROM A SECTION OF RED MARROW OF A HUMAN BONE. 

 a, giant cell; b, leukocytes; c, nucleated red blood cells; d, mitosis in a marrow 

 cell; e, outline of a fat cell; /, reticulum; g, mitosis in a giant cell. X 680. (After 

 Bohm and von Davidoff.) 



stroying worn-out red blood-corpuscles. In this process it is assisted 

 greatly also by the spleen and lymphoid organs generally. The phago- 

 cytic leukocytes of these locations are largely active in this destructive 

 process and in the transportation of the hemoglobin debris to the liver 

 where as hematoidin it is apparently appropriated in the manufacture 

 of the bile pigment, bilirubin. 



The generic name for the specific hemogenic cells of marrow is 

 myelocyte. This includes the parent blood-cell (hemoblast) and the 

 intermediate developmental stages of both white (lymphocytes, mono- 

 nuclear leukocytes leukoblasts) and red (megaloblast, normoblast, 

 erythroblast stages) cells. Besides these, there are of course abundantly 

 present also the adult forms of blood -cells both white (eosinophil, neu- 

 trophil, and basophil polymorphonuclear leukocytes, and lymphocytes) 

 and red (erythroplastids). Potential osteoblasts and osteoclasts are 



