DESCRIPTION OF THE PLATES. 



29 



deciduous and permanent teeth, nat. size. 

 In both figures, i 1, is crown of first 

 upper permanent incisor ; i 2, second 

 permanent incisor ; c, permanent canine ; 

 p 1 , first premolar ; p 2, second pre- 

 molar ; m 1 , first permanent true molar ; 

 m 2, second permanent true molar. The 

 germs of the permanent teeth are not 

 exposed in the lower jaw. Fig. 3. 

 Grinding surface of first and second 

 upper true molars, in different states 

 of abrasion of a New Zealander. Fig. 4. 

 The corresponding molars of the lower 

 jaw. Original. 



PLATE 121. 



Fig. 1. Side view. Fig. 2. Front view 

 of the deciduous and permanent teeth 

 in the jaws of a child of six years and a 

 half: nat size, i 1, first permanent in- 

 cisor ; i 2, second incisor ; c, canine ; 

 p 1, first premolar or bicuspid; p 2, 

 second premolar ; m I, first true molar ; 

 m 2, second true molar. Original. 



PLATE 122. 



Structure of the Human Teeth. Fig. 1 . 

 A longitudinal section, from side to side 

 of a middle lower incisor. 1 a. a trans- 

 verse section across the line traversing 

 fig. 1. Fig. 2. A longitudinal section, 

 from before backwards, of a middle lower 

 incisor. 2 a, a transverse section across 

 the line traversing fig. 2. 2 b, a trans- 

 verse section across the line. Purkinje 

 and Fraenkel. Fig. 3. A longitudinal 

 section, from before backwards, of a 

 lower canine. 3 a, a transverse section, 

 across the line traversing /#. 3. Retzius. 

 Fig. 4. A longitudinal section of a lower 

 premolar, or bicuspis. 4 a, a transverse 

 section through the fang, Purkinje. 

 Fig. 5. A transverse section of the 



dentine of a bicuspis with undivided 

 pulp-cavity, Retzius. Fig. 6. A longi- 

 tudinal section of a lower molar, nat. 

 size, showing the general course of the 

 dentinal tubes. Leeuwenhoek. Fig. 7. 

 A longitudinal section of a molar. Fig. 8. 

 A transverse section of the root of the 

 canine of an aged person, showing hyper- 

 thropy of the cement, Retzius. Fig. 9. 

 A longitudinal section of a lower incisor, 

 which, with fig. 6, gives the scale on 

 which the other figures are magnified. 

 The following letters indicate the same 

 parts in each of the above figures ; 



c, cement ;, d, dentine ; e, enamel ; e' 

 dusky longitudinal striae of enamel ; 

 /, contour lines of dentine ; o, osteo- 

 dentine ; v, vascular or pulp- cavity. 



PLATE 122. A. 



Fig. 1. — Portion of a transverse section of 

 the crown of a Human tooth, showing at 



d, the divided extremities of the dentinal 

 tubes ; and at e the wavy transverse 

 fibres of the enamel and the flexuous 

 fissures near the dentine. Fig. 2. A 

 section taken, almost parallel with the 

 outer surface of the enamel, near its 

 dentinal surface, showing the arrange- 

 ment of the fibres of the enamel according 

 to the length of the tooth, and the 

 rhomboidal figure of the obliquely cut 

 ends of the enamel-fibres. Purkinje and 

 Fraenkel. Fig. 3. Part of a section 

 almost vertical to the outer surface of 

 the enamel and parallel with its fibres, 

 showing their transverse markings (Ret- 

 zius) : magnified 350 linear dimensions. 

 Fig. 4. A small part of a transverse 

 section of dentine, magnified to the 

 same degree ; a, area of dentinal tube ; 

 b, parietes of ditto; i, intertubular space. 

 Fig. 5. Portions of five dentinal tubes 



