386 THE SUPPORTING TISSUES. 



extracted with a 0.5 per cent, solution of caustic alkali, to remove 

 the chondromucoid, and the free chondroitin-sulplmric acid. The 

 remaining material is then washed with water and boiled with 

 water in a Papin digester. Any collagen that may be present is 

 thus dissolved, while the albuminoid together with the cartilage-cells 

 remains behind. 



Mineral Constituents. Among the mineral constituents of car- 

 tilage, the very large amount of alkaline sulphates is especially 

 noteworthy. These are supposedly not present in the free state, 

 however, beyond traces perhaps, but result from the chondroitin- 

 sulphate on incineration. In the cartilage of the shark, very curi- 

 ously, sodium chloride constitutes as much as 94.2 per cent. "of the 

 total amount of mineral ash. As this represents 17.7 per cent, of 

 the moist material, the amount of sodium chloride would be suffi- 

 cient to form a concentrated solution in the cartilage, which, of 

 course, is scarcely conceivable as occurring in living tissue. It is 

 hence assumed that the salt is present in organic combination, but 

 of its pairling nothing definite is known. According to Bunge, such 

 large amounts of sodium chloride are also found in mammals during 

 the period of intra-uterine life and shortly after birth, and he be- 

 lieves that this is in accordance with the biogenetic law which under- 

 lies the development of the higher forms of life from those of a 

 lower order. 



With the appearance of old age a gradual deposition of calcium 

 salts occurs in the matrix of the cartilage, so that partial ossifica- 

 tion takes place. This, of course, also occurs during the develop- 

 ment of normal bone, but it is to be noted that, in contradistinction 

 to true bone, the matrix of senile, ossified cartilage retains its 

 original characteristics. 



BONE. 



The matrix of bone-tissue, like its contained fibrils, is com- 

 posed of collagen, which is here termed ossein, and is supposedly 

 identical with the common form that is obtained from connective 

 tissue. Of the composition of the cells, viz., the so-called bone- 

 corpuscles, nothing is known. With their processes they occupy the 

 lacunae and canaliculi, and are separated from the bony structure 

 proper by a layer of a very resistant albuminous substance of 

 unknown character. 



In contradistinction to the other supporting tissues of the body 

 which have thus far been considered, bone-tissue apparently con- 

 tains no glucoproteids. 



The function of the bone-tissue, as the principal supporting tissue 

 of the body, finds its expression in the preponderance of the mineral 

 constituents over the organic solids, and it is interesting to note that 

 the ratio between the two is fairly constant, not only in different 

 bones, but also in different animals. These salts are largely repre- 

 sented by calcium phosphate and carbonate, which impregnate the 



