DENTINE 285 



specially arranged connective-tissue fibres. Thin sections of 

 freshly-fixed preparations of the teeth of the Hake, which 

 had not been decalcified and were prepared by the Weil 

 process, confirmed the author's conclusions, as neither these 

 nor the earlier preparations showed any nuclei in the layer, 

 and its connexion with the connective tissue of the pulp was 

 quite evident. As further evidence of the nature of this 

 bordering layer, the teeth of the Hake often break up in 

 the direction of the bordering fibres, and this splitting 

 appears to be continuous with them. 1 



The Calcification of Osteodentine. From the great simi- 

 larity of osteodentine to bone we should expect to find 

 a similar mode of development to that of membrane bone. 



In osteodentine there is no separate pulp cavity, but 

 medullary spaces traversed by trabeculoe of bony substance. 

 The spiculse or trabeculse are clothed with cells in every 

 way resembling osteoblasts ; they are continuous with 

 bundles of connective-tissue fibres, and at the junction of 

 the tooth with the bone of attachment these trabeculae 

 become incorporated with the bone tissue of which they 

 form a part. The development is in every respect similar 

 to that of bone in membrane, and the connective-tissue 

 bundles become incorporated in the calcified tissue as 

 Sharpey's fibres do in bone. 



It is thus seen that orthodentine, vasodentine, and osteo- 

 dentine are all calcified on a connective-tissue foundation, 

 and as Tomes says : ' The development of the several 

 varieties of dentine which seem to run into one another 

 structurally by almost imperceptible gradations comes into 

 line and so seems more intelligible.' 



1 As pointed out on p. 256, the teeth of the Hake are often seen to break 

 up in a transverse direction as well, following the transverse lamination 

 of the dentine. 



REFERENCES 



1. Bennett, F. J. ' On certain Points connected with the Structure of 



Dentine.' Trans. Odontol. Soc. Great Brit., vol. xxi, p. 6, 1889. 



2. v. Bibra. See ref. on p. 117. 



3. Black, G. V. ' An Investigation of the Physical Characters of the 



Human Teeth in Relation to their Diseases.' Dental Cosmos, May 

 1895, vol. xxxvii, p. 353 et seq. 



