ii2 THE CHEMISTRY OF THE TISSUES AND ORGANS. 
From a large number of analyses, Hoppe-Seyler gives the following 
figures representing percentages of the total ash : — 
Ca. P0 4 . CO.. Fl. Mg. CI. 
38-49 54-46 6*24 1-28 0-44 0-19 
From his own numbers, Zalesky has calculated the probable composition 
of the mineral constituents of bone as follows : — 
Calcium phosphate . . . 83*889 
,, carbonate . . . 13 - 032 
Calcium in combination with fluorine, 
chlorine, etc. .... O350 
Fluorine 0-229 
Chlorine 0483 
Hoppe-Seyler considered that the characteristic inorganic ingredient of 
bone, dentine, and enamel is one analogous to apatite. Apatite has the 
formula Ca 10 Fl 2 (PO 4 ) 6 , or Ca 10 Cl 2 (PO 4 ) 6 . Very small quantities of these 
substances, however, occur in bone ; the chief compound is one in which C0 3 
takes the place of the Fl., or Cl 2 , namely, Ca lu C0 3 (P0 4 ) (3 . See, however, 
Gabriel's researches below. 
Tooth. — The calcareous tissues of tooth are dentine, enamel, and 
crusta petrosa. The last named is bone ; dentine is chemically similar 
to bone. Enamel, though epithelial in origin, may he conveniently 
taken here. 
Dentine. — This consists of water 10 per cent., and solids 90 per cent. 
The solids are organic and inorganic. The organic solids are less 
abundant than in bone. They consist of collagen and elastin; the latter 
form the lining of the dentinal tubules. From Aeby's analyses, Hoppe- 
Seyler gives the following table: — 
Ca 10 CO 3 (PO 4 ) 6 . . . 72-06 per cent. 
MgH(P0 4 ) .... 0-75 
Organic substances . . 27*70 ,, 
Enamel — This is the hardest tissue in the body. Hoppe-Seyler's 
quantitative analyses give the following mean result: — 
Ca 10 CO 8 (PO 4 ). . . . 96-00 per cent. 
RfgHP0 4 . . . 1*05 
Organic substances . . 3-60 ,, 
Various other investigators give numbers varying from 2 to 10 per 
cent, of organic matter. This they estimate by loss on ignition. Tomes, 1 
however, has recently shown that this loss is chiefly if not wholly due 
to water. On attempting to estimate the organic matter directly, 
none was found, or a quantity too small to he weighed. 
Gabriel 2 has recently worked at the question of the constitution of 
the mineral matter of bones and teeth. Some of his conclusions do 
not accord with the older work of Hoppe-Seyler. He rinds that the 
constituents are water, lime, magnesia, potash, soda, phosphoric acid, 
carbonic anhydride, chlorine, and fluorine. The quantities of lime 
and phosphoric acid, which are the most abundant constituents, vary 
1 Journ. Physiol., Cambridge and London, 1896, vol. xix. p. 217; Trans. Odont. Soc. 
Gr. Brit.. London, 1896. p. 114. 
- Ztschr. f. physiol. Chem., Strassburg, Bd. xviii. S. 257. 
