THE TEETH. 



471 



again only in its outer half or third ; the ramifications appearing, in the 

 root, as fine twigs given off from the principal canal, while in the crown, 

 they more resemble dichotomous divisions. In the latter case, they are for 

 the most part rare, in the former, it is otherwise ; the branches, which 

 are usually close together and given off at right or acute angles from 

 the trunk canal, having sometimes the appearance of a feather, some- 

 times that of a brush, the latter being most common when the twigs are 

 large and undergo further branchings. According to their more or less 

 frequent ramification, are the ends of the dentinal canals more or less 

 fine ; frequently appearing merely as excessively fine, pale lines, like 

 fibrils of connective tissue, and finally disappear. When they are dis- 

 tinct, they either become lost upon the surface of the dentine in a gra- 

 nular layer, which we shall have to consider presently, or they enter the 

 innermost portions of the enamel and cement, or finally they are con- 

 nected in pairs by loops in the dentine (terminal loops of the dentinal 

 canals). The branches of the principal canals are, almost always, very 

 fine and usually simple, though sometimes ramified ; they serve, as may 

 be best seen in the root, where they are excessively numerous, to con- 

 nect neighboring or even distant canals ; such anastomoses having either 

 the form of simple, transverse canals or of loops. The ultimate branches 

 present the same relations as the forked or simple terminations of the 

 principal canals, and end either free or by loops, in the dentine, or are 

 continued beyond it. 



The chemical composition of dried dentine is, according to Von 

 Bibra : 



Molar of a 

 Woman of 25. 



Phosphate of lime, with some fluoride 



of calcium, 



Carbonate of lime, .... 

 Phosphate of magnesia. 



Salts, 



Cartilage, 



Fat, 



Organic substance, 

 Inorganic substance, 



100-00 



21-00 

 79-00 



Molar of a 

 Man. 



66-72 

 3-36 

 1-08 

 0-83 



27-61 

 0-40 



100-00 



28-01 

 71-99 



Incisor of the 

 same Man. 



28-70 

 71-30 



In fresh teeth, Pepys found 28 p. c. cartilage, 62 inorganic matter, 

 10 water and loss ; and according to Tomes, teeth, after the pulp is 

 removed, lose in drying J T V of their weight. The organic basis of 

 the teeth, which may readily be obtained by treating them with hydro- 

 chloric acid, is identical in all respects with that of the bones, and is 

 readily changed into gelatin by boiling. This so-called cartilage of 



