TOOTH-STRUCTURE. 557 



found a changed relation between the Ca and phosphoric acid in osteo- 

 malacia. 



Rachitic bones are always poorer in mineral substances than normal bones. 

 The relation between Ca,P0 4 and C0 2 was found by GASSMANN to be the same 

 as in normal bones while he found a pathological increase in the magnesium. The 

 organic substance was found in rachitis to be relatively as well as absolutely 

 increased, at least in certain cases (GASSMANN). The statements differ in 

 regard to the water content. According to BRUBACHER this is larger while accord- 

 ing to GASSMANN it is 10 p. m. smaller than in normal bones. In opposition to 

 rachitis, osteomalacia is often characterized by the considerable amount of fat 

 in the bones, 230-290 p. m., but as a rule the composition varies so much that 

 the analyses are of little value. In a case of osteomalacia, CHABRIE l found a 

 larger quantity of magnesium than calcium in a bone. The ash contained 417 

 p. m. phosphoric acid, 222 p. m. lime, 269 p. m. magnesia, and 86 p. m. carbon 

 dioxide. MCCRUDDEN found more magnesium than calcium; other investigators 

 have on the contrary found more calcium than magnesium. 



The tooth-structure is closely related, from a chemical standpoint, 

 to the bony structure. 



Of the three chief constituents of the teeth dentin, enamel, and 

 cement the cement is to be considered as true bony structure, and as 

 such has already been discussed to some extent. Dentin has the same 

 composition as the bony structure, but contains somewhat less water. 

 The organic substance yields gelatin on boiling; but the dental tubes 

 are not dissolved, therefore they cannot consist of collagen. In dentin 

 260-280 p. m. organic substance has been found. Enamel is an epithe- 

 lium formation containing a large proportion of lime-salts. Correspond- 

 ing to its character and origin, the organic substance of the enamel 

 does not yield any gelatin. Completely developed enamel contains 

 the least water, the greatest quantity of mineral substances, and is the 

 hardest of all the tissues of the body. In full-grown animals it con- 

 tains hardly any water, and the quantity of organic substance amounts 

 to only 20-40-68 p. m. The relative amounts of calcium and phosphoric 

 acid are shown by the analyses of HOPPE-SEYLER to be about the same 

 as in bone-earths. The quantity of chlorine according to him is remark- 

 ably high, 0.3-0.5 per cent, while BERTZ 2 found that the ash of enamel 

 was free from chlorine and that dentin was very poor in chlorine. 



CARNOT, S who has investigated the dentin from elephants, has found 4.3 p. m. 

 calcium fluoride in the ash. In ivory he found only 2 p. m. Dentin from 

 elephants is rich in magnesium phosphate, which is still more abundant in ivory. 



1 Gassmann, Zeitschr. f. physiol. Chem. 70; Brubacher, Zeitschr. f. biol. 27. See 

 also Cappezzuoli, Bioch. Zeitschr. 16; Chabrie, Les phe"nom6nes chim. de I'ossification, 

 Paris, 1895, 65. 



2 See Maly's Jahresber., 30. 



3 Compt. Rend., 114. 



