CONNECTIVE TISSUES TEETH. 



79 



central rod always remains uncalcificd. The layers of matrix immediately 

 surroundin.tr the fibres undergo conversion into elastic tissue, and form the 

 dental sheaths of Neumann. Each dentinal tube is thus made up of several 

 odontoblasts arranged end to end. The formation of the cement is identical^ 

 with the process of intramembranous ossification in bone. The matrix of 



FIG. 42. 



Successive stages of the Development of the Deciduous or Temporary Teeth, and of the origin ot 

 the capsules of the Permanent set: a, piiniitive dental groove, seen in transverse section ; b, origin of 

 dental papilla from its floor, the pit being, in the recent state, roofed in by, and filled with, epithelium 

 cells- c, papilla projecting from the mouth of its follicle; d, e, formation of the opercula, which meet 

 over the papilla ; f, incipient formation of cavity of reserve ; g, h, i, formation of capsules and papilla? 

 of permanent teeth from cavity of reserve, and eruption of milk teeth. 



the cement is the loose myxomatous connective tissue of the dental alveoli 

 immediately surrounding the teeth. 1 As early as the fifth month, before the 

 calcification of the primitive pulps commences, a provision is made for the 

 production of the "permanent" teeth, the capsules of which originate in 

 buds or offsets from the upper part of the capsules of the "temporary" or 

 milk teeth (/, Fig. 42). These offsets are at first in the condition of open 

 follicles communicating with the cavity of the primitive tooth ; but they are 

 gradually closed in, and detached altogether from the capsules of the milk 

 teeth (y, h, i). The three permanent molars, which are super-added in the 

 adult to the milk teeth of the infant, are produced by a precisely similar 

 process of budding from the sac detached from that of the last milk molar. 

 The following are the principal dates connected with the development and 

 eruption of the teeth : 



1 For a full account of the structure and development of the teeth, see Waldeyer's 

 Essay in Strieker's Human and Comparative Histology, 1870 ; Syd. Soc. Trans. 

 vol. i, p. 403, to which an excellent bibliography is attached. Also Quain and 

 Sharper, vol. ii, p. 780. Wenzel, Pamphlet, Leipzig, 1871. For the resorptiou of 

 parts of the teeth see Kolliker, Centralblatt, 1872, pp. 353 and 369. 



