THE DENTAL TISSUES. 



87 



the Flounder teach that hard dentine and vaso-dentine are 

 not very dissimilar in their nature, and that the one passes by 

 imperceptible gradations into the other, the dentine at the 

 base of the Flounder's tooth provides us with an example of 

 typical vaso-dentine : that is to say, dentine in which the 

 dentinal tubes are quite absent, having had their place 

 taken by a complete system of vascular channels. 



The teeth of the Ostracion (Fig. 45), or of the Hake 

 (Figs. 46 and 86), afford good examples of this form of tissue. 



FIG. 46 ( l ). 





The matrix is solid, so far as penetration by fine tubes 

 goes, but it contains a system of larger canals which carry 

 only blood, and no pulp tissue, out to near the surface of 

 the dentine, where they form a plexus. 



I have not been able to satisfy myself of the existence of 

 any definite structure in the matrix; sometimes it looks 

 granular, and sometimes has a finely reticulated look, re- 

 calling the appearances described by Bodecker in human 

 dentine. (See page 68.) 



( l ) Section of Dentine from a freshly caught Hake (Merlucius). d, 

 Dentine matrix ; cp, Capillary blood-vessels hanging out from its edge, 

 containing here and there abundant blood- corpuscles. 



