470 



SPECIAL HISTOLOGY. 



The dentinal canals present certain constant peculiarities in their 

 course which may be best gathered from Figs. 185 and 187; it is not 

 straight but tvavT/, and in addition, thej present numerous rayniji- 



Fig. 1S5. Fi-. 1S6. 



catioris and anastomoses. Each canal 

 describes, in general, two or three large 

 curvatures, and a very great number (as 

 many as 200 in 1 line, according to 

 E,etzius) of small curvatures, which are 

 sometimes more or less strongly marked 

 and occasionally have even the appear- 

 ance of actual zigzags, or spiral wind- 

 ings. The ramifications of the canals 

 (Figs. 185 and 186), appear in the first 

 place as divisions, and then as true rami- 

 fications ; 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 somewhat narrowed after 

 division, then run close together and tole- 

 rably parallel, towards the surface of the 

 dentine, and excepting in the root, branch 



Fig. 1S5. — Dentinal tubules I'lom the root, magnified 3'iO diameters: a, internal surface of 

 the dentine, with scattered canals; /;, their divisions; c, terminations with loops; rf, granu- 

 lar layer, consisting of small dentinal globules at the boundary of the dentine; e, bone 

 lacuncE, one anastomosing with dentinal canals. From Man. 



Fig. 18G. — Transverse section through the dentinal canals of the root, a, in order to ex- 

 hibit their excessively numerous anastomoses ; magnified 350 diameters. From Man. 



