174 



ON THE ELEMENTARY PARTS Of THE HUMAN FABUIC. 

 [Fig- 6 9- [Fig. 70. 



A view of an Incisor and of a Molar Tooth, 

 given by a longitudinal section, and showing 

 that the enamel is striated, and that the strias 

 are all turned to the centre; the internal 

 structure is also seen ; 1, the enamel ; 2, the 

 ivory ; 3, the cavitas pulpi.] 



209. The Enamel is composed 

 an inch in diameter, arranged side 



[Fig. 71. 



A vertical section of an adult Bicuspid, cut from 

 without inwards magnified 4 times; 1, 1, the cor- 

 tical substance which surrounds the root up to the 

 commencement of the enamel; 2, 2, the ivory of 

 the tooth, in which are seen the greater parallel 

 curvatures, as well as the position of the main 

 tubes; 3, apex of the tooth, where the tubes are al- 

 most perpendicular ; 4, 4, the enamel ; 5, the cavity 

 of the pulp, in which are seen, by means of the 

 glass, the openingsof the tubes of the dental bone.] 



of solid prisms or fibres, about l-5600th of 

 by side, and closely adherent to each other ; 



[Fig. 72. 



A vertical section of an imperfectly developed Incisor, 

 taken from the follicle in wliicli it was enclosed; this 

 section is meant to show the position of the enamel 

 fibres, and also that a part of the appearances which are 

 seen in this substance under a less magnifying power, 

 originate in parallel curvatures of the fibres; 1,1, the 

 enamel ; 2, 2, the dental bone, or ivory; 3, 3, the minute 

 indentations and points on the surface of the ivory, on 

 which the enamel fibres rest ; 4, 4, brown parallel fibres; 

 5, parallel flexions of the fibres of the dental bone in these 

 stripes ] 



A portion of the surface of the Enamel 

 on which the hexagonal terminations 

 of the fibres are shown highly magni- 

 fied; 1, 2, 3, are more strongly marked 

 dark crooked crevices, running be- 

 tween the rows of the hexagonal 

 fibres.] 



