88 



OSTEOLOGY 



but the great majority are roundish nucleated cells, the true "marrow cells'* 

 of Kolliker. These marrow cells proper, or myelocytes, resemble in appearance 

 lymphoid corpuscles, and like them are ameboid; they generally have a hyaline 

 protoplasm, though some show granules either oxyphil or basophil in reaction. 

 A number of eosinophil cells are also present. Among the marrow cells may be 

 seen smaller cells, which possess a slightly pinkish hue; these are the erythroblasts 

 or normoblasts, from which the red corpuscles of the adult are derived, and which 

 may be regarded as descendants of the nucleated colored corpuscles of the embryo. 

 Giant cells (myeloplaxes, osteoclasts) , large, multinucleated, protoplasmic masses, 

 are also to be found in both sorts of adult marrow, but more particularly in reel 

 marrow. They were believed by Kolliker to be concerned in the absorption of 

 bone matrix, and hence the name which he gave to them osteoclasts. They 

 excavate in the bone small shallow pits or cavities, which are named Howship's 

 foveolae, and in these they are found lying. 



Normoblast with dividing nucleus 



Myelocyte 



Erythrocyte ~'^ff^.j\(" 



Myeloplaxe fs-i^r: 



Myelocyte 



Fat 



__ Eosinophil 

 cell 



Li.1- Normoblasts 



Myelocyte 

 dividing 



- Myelocyte 



-Fat 



FIG. 72. Human bone marrow. Highly magnified. 



Vessels and Nerves of Bone. The bloodvessels of bone are very numerous. Those 

 of the compact tissue are derived from a close and dense network of vessels ramify- 

 ing in the periosteum. From this membrane vessels pass into the minute orifices 

 in the compact tissue, and run through the canals which traverse its substance. 

 The cancellous tissue is supplied in a similar way, but by less numerous and larger 

 vessels, which, perforating the outer compact tissue, are distributed to the cavities 

 of the spongy portion of the bone. In the long bones, numerous apertures may 

 be seen at the ends near the articular surfaces; some of these give passage to the 

 arteries of the larger set of vessels referred to; but the most numerous and largest 

 apertures are for some of the veins of the cancellous tissue, which emerge apart 

 from the arteries. The marrow in the body of a long bone is supplied by one 

 large artery (or sometimes more), which enters the bone at the nutrient foramen 

 (situated in most cases near the center of the body), and perforates obliquely the 

 compact structure. The medullary or nutrient artery, usually accompanied by one 

 or two veins, sends branches upward and downward, which ramify in the medul- 

 lary membrane, and give twigs to the adjoining canals. The ramifications of this 



