THE TEETH. 



481 



white cartilage remaining, which may easily be separated from the den- 

 tine, and usually, when boiled, yields gelatin. 



Like bone, the cement consists of matrix and of lacuncp, but rarely 

 contains Haversian canals and vessels. Besides these, peculiar canals 

 aiuiloirous to those of the dentine are found, and other more abnormal 



cavities 



The matrix is sometimes granular, sometimes transversely striated, 

 sometimes amorphous, and frequently laminated like bone. The lacunce 



Fisr. 192. 



resemble in all essential characters those of the bones, so that any de- 

 tailed description may be dispensed with. They are distinguished only 

 by the great variety which they present in number, form, and size (0-005- 

 0*02, even to 0'03 of a line), and the unusual number and length (as much 

 as 0"03 of a line), of their canalieuli. The majority are oval, and lie 

 parallel to the axis of the tooth, others are rounded and pyriform. Those 

 are most remarkable which have a very elongated form, together with a 

 narrow, canal-like cavity (Fig. 185), inasmuch as their resemblance to 

 the dentinal canals is unmistakable. The canalieuli often resemble 

 feathers and brushes, and unless the lacunce are altogether isolated, 

 connect them with one another, and anastomose with the ends of the 

 dentinal canals. In the thinnest part of the cement, towards the crown, 

 the lacunce are invariably absent ; they are first met with, as a rule, 

 about the middle of the fang, but are here scattered and solitary ; towards 

 the extremity their number gradually increases, and they not unfre- 

 quently take on a very regular arrangement, as in the external layer of 

 the long bones, lying in series in the layers of the cement, and sending 

 most of their canalieuli inwards and outwards, so as to give rise to an 

 even, fine, transverse striation of the cement. The thicker layers of 



Fig. 1D2. — Dentine and cement from tbe middle of the fang of an incisor tooth: a, dentinal 

 canals; b, interglohular spaces, having the appearance of osseous lacuna; c, smaller inter- 

 globular spaces; d, commencement of the cement, with many canals close together; e, its 

 lameUa ; f. lacunce; g, canals; from Man. Magnified 350 diameters. 



31 



