24 METABOLISM OF ORGANIC AND INORGANIC PHOSPHORUS. 



in which the mineral bodies of the bony structure are combined with 

 each other. Chlorin and fluorin are present in the same form as in 

 apatite (CaFl 2 , 3Ca3P 2 O 8 ). If the magnesium, chlorin, and fluorin be 

 eliminated, the last according to Gabriel occurring only as traces, the 

 remaining mineral bodies form the combination 3(Ca 3 P 2 O 8 )CaCO 3 . 

 According to this author the simplest expression for the composition 

 of the ash of the teeth is (Ca 2 (PO 4 ) 2 + Ca 5 HP 3 O 13 + H 2 O), in which 2 to 



3 per cent of the lime is replaced by magnesia, potash, and soda, and 



4 to 6 per cent of the phosphoric acid by carbon dioxid, chlorin, and 

 fluorin. Analyses of bone earths have shown that the mineral con- 

 stituents exist in rather constant proportions, which is nearly the 

 same in different animals. The diverse quantitative composition of 

 the various bones of the skeleton depends probably on the varying 

 quantities of other formations, such as the marrow, blood vessels, etc., 

 which they contain. This probably also explains the larger quantity 

 of organic substance in the spongy parts of the bones as compared 

 with the more compact parts. Schrodt a has made comparative analy- 

 ses of different parts of the skeleton of the same animal (dog), and 

 has found an essential difference. The quantity of water in the fresh 

 bones varies from 138 to 438 parts per thousand. The composition 

 of bones at different ages has not been definitely determined, but 

 according to the analyses made by Voit 6 of bones of dogs and by 

 Brubacher c of the bones of children it appears that the skeleton be- 

 comes poorer in water and richer in ash with increase in age. Grafen- 

 berger d has found that the bones of rabbits from 6^ to 7J years old 

 contained only 14 to 17 per cent of water, while the bones of full 

 grown rabbits from 2 to 4 years old contained 20 to 24 per cent. The 

 bones of old rabbits contain more carbon dioxid and less calcium 

 phosphate than do those of young ones. 



CALCIUM METABOLISM. 



A great many experiments have been made to determine the change 

 in the bone constituents, for instance, when a ration rich in lime 

 and one deficient in lime is fed, but the results have always been inde- 

 cisive or contradictory. The attempts to substitute other alkaline 

 earths or clay for the lime of the bones have also given unsatisfactory 

 results. Weiske e has shown that when young and still rapidly grow- 

 ing rabbits are fed w T ith oats, which are poor, in acid and lime, plus 

 magnesium and strontium carbonate, these substances in part pass 

 into the skeleton, but a physiological replacement of lime by magne- 

 sium or strontium is not to be expected. On the administration of 



Maly's Jahres-Ber., 1877, 6 : 207. * Maly s Jahres-Ber., 1891, 21 : 290. 



1> Zts. Biol., 1880, 16 : 55. e Abs., Chem. Centrbl., 1892 (2), p. 590. 



e Ibid. /1890, 27:517. 



