Quain's elements of anatomy . their inner and largerend is irsVo^h of an inch, andthe distance between adjacent tu-bules is commonly about two or three times their width. From theirsides, numerous immeasurably fine branches are given off, which penetratethe hard intertubular substance, where they either anastomose or termi-nate blindly. These lateral ramuscles are more abundant in the the periphery of the ivory the tubules, which by division andsubdivision have become very fine, terminate imperceptibly by free ends. The tubules have each a proper wall (dentinal slieatli) independent
Quain's elements of anatomy . their inner and largerend is irsVo^h of an inch, andthe distance between adjacent tu-bules is commonly about two or three times their width. From theirsides, numerous immeasurably fine branches are given off, which penetratethe hard intertubular substance, where they either anastomose or termi-nate blindly. These lateral ramuscles are more abundant in the the periphery of the ivory the tubules, which by division andsubdivision have become very fine, terminate imperceptibly by free ends. The tubules have each a proper wall (dentinal slieatli) independent of theintertubular matrix, but intimately adhering- to it. By steeping- sections ofdecalcified dentine in strong hydrochloric acid, the matrix is destroyed, and thesemembranous tubes, which consist of a more resisting material (probably elasticsubstance), remain behind. In the temporary, and sometimes even in the permanent teeth, the tubules areconstricted at short intervals, so as to present a moniliform character. The ter-. 552 THE TEETH. minal branches of tubules are occasionally seen to pass on into the cement whichcovers the fang, and to communicate with canaliculi proceeding from thecharacteristic lacunEB found in that osseous layer. Tubules have likewise beenobserved by Tomes passing into the enamel in the teeth of marsupial animals,and in a less marked degree, in human teeth. Fig. 474. Fig. 474.—Sections op dentinal tubules (after Fraenkel). a, cut across ; h, cut obliquely. (About 300 diameters.) The interhibular substance is translucent. Theanimal matter which remains, after the earth hasbeen removed by an acid, may be torn into laminas(Sliarpey), parallel with the internal surface of thepulp-cavity, and therefore across the direction of thetubules. According to Ebner the matrix contains finefibrils like those of the matrix of bone. The laminated structure Is an indication of the deposition of dentinal substancein successive strata in the process of formation of the
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Keywords: ., boo, bookcentury1800, booksubjectanatomy, booksubjecthumananatomy
