616 



THE TEETH. 



into basis-substance and not calcined. The dentinal fibers enter the bioplas- 

 son bodies, and each fiber is united with the net-work of these bodies by 

 means of delicate, thorn-like projections. At other times the basis-substance 

 of the dentine is developed within the interglobular spaces, but devoid of 

 lime-salts. In this instance the dentinal fibers, without investment and with- 

 out changing their course, pierce the basis-substance and send offshoots to 

 this through the surrounding light spaces. 



The dentine shows peculiar formations in general, though not constantly, 

 as instanced when approaching the enamel and cementum. These formations, 

 however, being in close relation to the covering tissues of the tooth, I prefer 

 to describe in the chapter on cementum and enamel. 



Cementum. It has been long known that there exists a striking analogy 

 between the structures of the cementum and bone. 



If we consider the central or pulp canal of the tooth as a formation anal- 

 ogous to a Haversian canal, containing blood-vessels, nerves, and medullary 

 tissue, then the surrounding cementum corresponds to a Haversian system of 

 ordinary bone, between which and the pulp-canal there exists an intermediate 

 stratum of dentine. 



FIG. 263 A. CROSS-SECTION OF 

 DENTINE OF INCISOR. STAINED 

 WITH CHLORIDE OF GOLD. MAIN 

 MASS OF DENTINE. 



F, dentinal canaliculi with the central 

 dentinal fiber, the latter with star-like off- 

 shoots ; R, the basis-substance between the 

 canaliculi, pierced by a delicate light net- 

 work. Magnified 2000 diameters. 



R 



FIG. 263 B. CROSS-SECTION OF 

 DENTINE OF INCISOR. STAINED 

 WITH CHLORIDE OF GOLD. VIEW 

 FROM OUTER PERIPHERY OF DEN- 

 TINE, NEAR ENAMEL. 



F, dentinal canaliculi with the central 

 dentinal fibers, the latter with star-like oft'- 

 shoots ; -K, the basis-substance between the 

 canaliculi, pierced by a delicate, light net- 

 work. Magnified 2000 diameters. 



The zone of dentine is not present all around the pulp-cavity on the apices 

 of the roots; there the cementum, being the outermost layer of the tooth, 

 directly lines the cavity. 



Delicate parallel striations are to be seen in the cementum, identical with 

 the lamellas of a Haversian system, and, as a rule, more plainly marked near 

 the periphery than toward the dentine. 



Within the basis-substance of the cementum there are numerous branching 

 spaces, in correspondence with the lacunae of bone. The offshoots of these 

 spaces in the cementum, like the spaces themselves, are very marked in dry 

 specimens, because of their being filled with air. In chromic acid specimens, 

 on the contrary, the offshoots are much less prominent, and the less the more 

 thoroughly the decalcification has been effected by the acid. No essential 

 difference is noticeable between the lacunae and canaliculi of ordinary bone 

 and those of the cementum ; in both tissues there exists a great variety as to 



