The Dental cosmos . Fig. 11.—Lacunae of the cement, showing their very minute branching canaliculi. 1000: 1. The tubules are narrower and more numerous than those of humandentine, and to this structural peculiarity the greater density andelasticity of ivory has been supposed to be due ; a view which, in ANATOMY AND PATHOLOGY OF THE TUSKS OF THE ELEPHANT. 423 part at least, does not seem to conform to the facts, since we haveseen that the density of ivory is less than that of human dentine. Itis also quite possible that the pronounced secondary curvatures of thetubuli may have more to do with t
The Dental cosmos . Fig. 11.—Lacunae of the cement, showing their very minute branching canaliculi. 1000: 1. The tubules are narrower and more numerous than those of humandentine, and to this structural peculiarity the greater density andelasticity of ivory has been supposed to be due ; a view which, in ANATOMY AND PATHOLOGY OF THE TUSKS OF THE ELEPHANT. 423 part at least, does not seem to conform to the facts, since we haveseen that the density of ivory is less than that of human dentine. Itis also quite possible that the pronounced secondary curvatures of thetubuli may have more to do with the elasticity of the tissue than theircloseness. The general directionof the tubules is perpendicular to the walls ofthe pulp-chamber, and therefore slightly inclined toward the apex ofthe tooth. They possess primary, secondary, and tertiary curvatures. Fig. 12. 1. Fig. 12.—Cross-section of cement, showing the marked gyrations of Sharpeys fibers, a,stratum granulosum ; b, dentine. 250 : 1. The primary curves are two in number : a short, distinct curve, con-vex toward the apex of the tooth, and a long, slightly marked curve,concave toward the apex (Fig. 13). In three of the six specimenswhich I examined the latter curve was entirely wanting, being replacedby a straight line. The secondary curves vary greatly in different tusks and in differ-ent portions of the same tusk, sometimes being short and abrupt,sometimes long and shallow or wavy. On the whole, the so-calledsecondary curvatures of the tubules of human dentine are in no wayto be compared to those of the tubules of ivory. 424 THE DENTAL COSMOS. Fig. 13. On cross-sections the tubules are seen to pass from the center of thetooth, radially, in an almost straight line toward the periphery ; notuntil about one-third of the distance has been passed do the gyrationsappear, and then continue to n
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