44 CONNECTIVE TISSUE. 



75 per cent, water and 25 per cent, solids ; the latter consisting 

 of salts, a very small amount of fat, and two proteids, one a cell- 

 globulin coagulating at 47-50 C. and a nucleoproteid containing 

 1.6 per cent, of phosphorus. Hemoglobin is also present. 



Marrow-cells (Fig. 36). The cells of red marrow are of four 

 kinds : 1. True marrow-cells, which are round, nucleated cells like 

 white blood-corpuscles, but larger, and exhibiting ameboid motion. 

 2. Erythroblasts, pinkish in color, and in appearance like the nucle- 

 ated red blood-corpuscles of the embryo. Some authorities regard 

 these latter as cells which are originally true marrow-cells and 

 afterward become red blood- corpuscles ; while others hold that 

 they are never marrow-cells, but have come directly from the 

 nucleated blood-cells of the embryo and become red blood- 

 corpuscles, the nuclei disappearing. In the erythroblasts the 

 process of karyokinesis may often be observed. 3. Myeloplaxes ; 

 these cells are also called giant cells, myeloplaques, and osteoclasts. 

 These are very large nucleated cells, which are also found in the 

 yellow marrow of the adult. 4. Cells which contain red blood- 

 corpuscles in various stages of transformation into pigment, resem- 

 bling the large cells found in the spleen, and called splenic cells. 



Blood-vessels of Bone. The periosteum sends branches of its 

 blood-vessels into the compact tissue, some passing into the Haver- 

 sian canals, while others continue on and supply the cancellous 

 tissue in the interior. In the middle of the long bones is an 

 opening, the nutrient foramen, through which passes the medullary 

 or nutrient artery, with one or two veins, traversing the compact 

 tissue to reach the medullary canal, where it supplies the tissue 

 contained therein. Similar openings exist in other bones for the 

 transmission of blood-vessels to their interior. It is claimed by 

 some that the walls of the capillaries in the marrow are imperfect, 

 and that through the openings which exist the red blood-corpuscles 

 produced in the marrow find their way into the blood-circulation. 



Lymphatic Vessels of Bone. These are found in the periosteum 

 and the bone-substance, and also in the Haversian canals. 



Nerves of Bone. The periosteum is supplied with nerves, and 

 they also pass into bones through the nutrient foramina. Espe- 

 cially rich in nerves are the articular extremities of long bones, 

 the vertebrae, and the larger flat bones. 



Chemical Composition of Bone. Hoppe-Seyler gives the follow- 

 ing analysis of undried bone without separation of marrow or blood : 

 Water 50.00 per cent. Ossein (or collagen) . . 11.40 per cent. 



Fat 15.75 



Bone earth. . .21.85 



The following is Zalesky's analysis of human dried macerated 

 bone : 



Organic constituents 34. 56 per cent. 



Inorganic " 65.44 " " 



100.00 



