184 OSSEOUS SYSTEM. [SECT.97. 



white colour, high specific gravity, and resistance to putrefaction, 

 to their inorganic components. The latter, being so intimately 

 blended with the animal constituents, protect these also; and, 

 accordingly, bones from ancient graves, and those of fossil animals, 

 still retain their original proportion of cartilage. 



The true cartilages, and also those of the foetus, contain, in 

 addition to their organic basis, 50 to 75 per cent, of water, and 

 3 to 4 per cent, of salts (chiefly salts of soda and carbonate of 

 lime, with a little phosphate of lime and magnesia). The organic 

 matter forming the matrix consists of chondrin, or cartilage-ge- 

 latine ; but the cartilage-capsules, and the cells which they enclose, 

 are insoluble in water, and resist the action of caustic potass and 

 sulphuric acid for a longer period than the matrix, so that their 

 composition appears to be different, and peculiar to themselves. 



§ 97. Vessels of the Bones and Accessory Parts. A. Blood- 

 vessels. — Besides the numerous vessels passing through it on 

 their way to the bones, the periosteum is furnished with a 

 moderately close network of capillaries, of 0"005"' in diameter, 

 situate chiefly in its outer layer. The blood-vessels proper to the 

 bone are very numerous, as may be seen in injected preparations, 

 and still more readily in fresh bones, in which they are filled with 

 blood. In the long bones, the medulla, the spongy articular ex- 

 tremities, and the compact substance of the shaft, are all nourished 

 by special vessels. Those of the medulla, or the vasa nutritia, pass 

 into the bones through special canals, one or two in number in the 

 diaphyses, but more numerous in the apophyses;" and, after be- 

 stowing a few small vessels to the innermost Haversian canals of 

 the compact substance, ramify in the medulla, and then form a 

 genuine network of capillaries, of 0'004-'" to 0^005 2'" in diameter. 

 The vessels of the compact substance come, for the most part, 

 from those of the periosteum, very soon lose their muscular coat, 

 and form in the Haversian canals, which are sometimes destitute 

 of other contents, sometimes contain a small quantity of marrow, 

 a network of wide canals. Of these canals, only a very small 

 number can be regarded as capillaries, seeing that the majority of 

 them possess a layer of areolar tissue and an epithelium, and that 

 fine capillaries are present only in the larger Haversian canals, 

 along with the main vessel. The venous blood passes out of every 

 long bone at three places: 1. by a large vein which accompanies 

 the arteria nutritia, and has the same distribution; 2. by numerous 

 large and small veins at the articular extremities; 3. by many 



