624 



THE TEETH. 



matter, in the shape of beaded fibers, where they form larger offshoots of the 

 plastids. Similar features are also present in the tissues of the tooth. 



(1) The dentinal canaliculi are excavations in the basis-substance of the den- 

 tine, each containing in its center a fiber of living matter. Besides the dentinal 

 canaliculi, there exists an extremely delicate net-work within the basis-substance 

 of the dentine, into which innumerable offshoots of the dentinal fibers pass. 

 Although we cannot trace the living matter throughout the whole npt-work in 

 the basis-substance, we are justified in assuming that not only the dentinal canal- 

 iculi, but the whole basis-substance of the dentine, is also pierced by a delicate 



net-work of living matter. The 



^l^^l^|^|^iBBBIHlilBBiBM]Bi|ii| living matter of the dentine is in 



'^ : ^^%^*'3~-'% ;; ^ direct union with that of the bio- 



^^^^'X |- \ . feji /, ^ pldxson bodies of the pulp, of the 



cementum, and of the enamel. 



Htete-^r '.-< . / V ^ ; ",-T' v-V (2) The cementum, as well as 



(~~Y? E'F ordinary bone, 7.v provided u'ith la- 



SfSlte^-' ?^/. 3 ( J cunce and canaliculi. The lacuna? 



contain nucleated plastids, and the 

 canaliculi hold offshoots of the liv- 

 ing matter of the plastids. The 

 whole basis-substance of the cemen- 

 tum is traversed by a delicate net- 

 work, which in all probability con- 

 tains living matter, though this is 

 traceable only in its thorn-like pro- 

 jections from the periphery of the 

 plastids and their larger offshoots. 

 The living matter of the cementum 

 is uninterruptedly connected with 

 that of the pericementum, and con- 

 tinuous ivitli the living matter of 

 the dentine, either through inter- 

 vening bioplasson bodies in the in- 

 terzonal layer, or directly with the 

 dentinal fibers. 



(3) The cementum covering the 



neck of the tooth is devoid of lamella? and plastids. It is built up by directly 

 ossified osteoblasts of the pericementum, presenting their prismatic shapes, and 

 everywhere traversed by a net-work of living matter. This is in connection with 

 the pericementum, and with the dentine mainly through the intervening net-work 

 in the basis-substance of the latter. 



(4) The enamel is traversed by fibers of living matter located in the inter- 

 stices between the enamel-rods. The fibers are connected with each other by delicate 

 fibrillw, piercing the enamel-rods in a vertical direction. The enamel-fibers send 

 conical thorns toward the enamel-rods, and such thorns are visible in all interstices 

 between the enamel-rods. Tlie enamel fibers are continuous on the outer surface 

 with the covering layer of flat epithelia, and on the inner surface with the dentinal 

 fibers. The latter connection is either direct or indirect through a net-work of living 

 matter, or through intervening bioplasson bodies in the interzonal layer. 



History. It is not my intention to traverse the entire history of micro- 

 scopical studies regarding the structure of teeth. I propose to quote only 



FIG. 270. UNION OF DENTINE WITH 

 ENAMEL. 



D, dentine; E, enamel; P, bioplasson formations 

 at the boundary between both tissues, in union 

 with enamel-fibers, EF, and with dentine-fibers, 

 DF. Magnified 1200 diameters. 



