SECT. I37.] THE TEETH. 29 1 



The course of the dentinal canals is not straight, but undulating ; 

 besides, they exhibit numerous ramifications and anastomoses. 



Each canal usually describes two or three large curves, and 

 a very large number (up to 200 in a line, Retzius) of small 

 flexures. The ramifications of the canals appear as divisions, and 

 also as true ramifications. The former are very Fi s- 121. 



frequently met with near to the origin of the 

 tubes from the dental cavity, and are almost 

 always bifurcations, which are repeated two 

 to five times or more, so that at length, 

 four, eight, sixteen, or more canals arise from 

 a single one. The canals, now narrower after 

 their division, run close together, and nearly 

 parallel towards the surface of the dentine, and, 

 except in the fang, first begin to send out 

 ramifications in the outer half or in the outer „ Transverse section 



through the dentinal 



third of their course. These ramifications ap- caMls of thc &"%• »u 



*■ order to show their 



pear in the fangs chiefly as fine branches issuing extremely numerous 



" _° anastomoses. Magni- 



from thc main tubes, but in the crown as bi- fled 350 times. Ofman. 

 furcated terminations of them. In the latter case they are for the 

 most part few in number ; it is otherwise on the fang, where the 

 branches, being generally close to each other, and passing off from 

 the canals at right or acute angles, give them sometimes the 

 appearance of a feather, sometimes of a brush ; the latter espe- 

 cially, when the branches are longer and ramify still more. Thc 

 terminations of the dental tubes are more or less fine according to 

 the number of their ramifications, and are frequently so very fine, 

 that they appear as extremely delicate, pale lines, like fibrils of 

 connective tissue, and are, at length, withdrawn from view. 

 "Wherever the terminations are distinct thev either reach the 

 surface of the dentine, where they partly end in a granular layer, 

 to be afterwards described, or pass into the innermost parts of 

 the enamel and cement ; or they join together in pairs in the 

 form of loops in the dentine itself {terminal loops of the dentinal 

 canals). The branches of the main canals are almost always very 

 fine, mostly simple, but sometimes branched, and, as can be best 

 demonstrated in the fangs, where they are unusually numerous, 

 serve to connect neighbouring or more remote canals, by ana- 

 stomoses in form either of transverse branches or of loops. Thc 

 final terminations present the same conditions as the bifurcated or 

 simple terminations of the main canals, and end either free or 

 with loops in the dentine, or extend beyond the latter. 



u 2 



