620 



THE TEETH. 



dentinal canaliculi, when approaching the periphery, become slightly dilated, 

 so as to produce slender, pear-shaped cavities, in accordance with which the 

 terminating dentinal fibers exhibit slight enlargements. 



The boundary between dentine and cementum presents a wavy line, 

 traversed by delicate threads, or occupied by spindle-shaped bioplasson for- 

 mations, all of which are in union with direct or indirect elongations of the 

 dentinal fibers. 



The cementum around the neck forms a narrow layer, which is cut off 

 obliquely at the place of junction with the enamel. Both the cementum and 

 enamel in this situation being of the same width are separated by a 

 boundary which runs from the outer periphery obliquely downward to the 

 dentine. This relation I found in the majority of teeth, and it is only 

 exceptionally that I have met with cementum overlapping the enamel. The 

 cementum on the neck is built up by delicate prisms, or spindles, arranged 



FIG. 266. ANOMALOUS FORMATION OF CEMENTUM ON THE 

 NECK OF A HUMAN TOOTH. 



D, dentine; N, cementum on neck of tooth, with spindle-shaped or prismatic fields of 

 basis-substance ; DP, depression in the cementum of the neck, filled with elements of peri- 

 cementum, P, surrounded upward by a zone of regularly developed cementum, Cc. Magnified 

 1200 diameters. 



vertically to the surface of the dentine. The prisms represent the fields of 

 the basis-substance, and are separated from each other by light rims, holding 

 beaded fibers, or traversed by delicate vertical threads. In transverse sec- 

 tions, when the prisms are cut obliquely, they exhibit irregular, opaque fields, 

 separated from each other by light rims. 



The cementum on the neck of the tooth is devoid of lamellse and lacunae, 

 which appear deeper below, together with all the characteristic features of 

 the fully developed structure of the cementum. The lamellse become the 



