THE TEETH. 43 



zigzags, or spiral windings. The ramifications of the canals (figs. 

 185 and 186), appear in the first place as divisions } and then as 

 true ramifications ; the former are very frequently to be met with 

 close to the origin of the tubules from the pulp cavity and 

 are almost always bifurcations, of such a kind that one canal 

 divides at an acute angle into two of almost the original diameter. 

 These divisions may be repeated 2 — 5 times altogether, and 

 even still oftener, so that at last, 4 — 8 — 16, and even more 

 canals, proceed from a single one. The canals, already some- 

 what narrowed after division, then run close together and 

 tolerably parallel, towards the surface of the dentine, and 

 excepting in the root, branch 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, sometimes 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 distinct, they either become lost upon the 

 surface of the dentine in a granular layer, which we shall 

 have to consider presently, or they enter the innermost por- 

 tions of the enamel and cement, or finally, they are connected 

 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 connect neighbouring 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 den- 

 tine, or are continued beyond it. 



The chemical composition of dried dentine is, according to 

 Von Bibra : 



