88 A MANUAL OF DENTAL ANATOMY. 



The arrangement of the vascular canals is regular and 

 striking, reminding one of the appearance of the capillary 

 network in an injected intestinal villus. In fact, an intes- 

 tinal villus petrified, whilst the capillary network remained 

 pervious and carried red blood circulating through it, would 

 form no bad representation of a conical vaso-dentine tooth. 



For these canals do actually contain capillaries, and blood 

 actively circulates through them; a section cut from the 

 fresh, brilliantly red tooth of a Hake often shows the coats 

 of the capillary hanging out from the edge, and the canals 

 full of blood-corpuscles (Fig. 46). 



In all vaso-dentine teeth with which I am acquainted the 

 pulp chamber is of simple form, the pulp coated by a distinct 

 layer of odontoblasts, and no pulp-tissue other than the 

 capillaries passing out into the dentine, so that each capil- 

 lary fits and wholly fills its channel in the dentine. 



Vaso-dentine is less dense and hard than ordinary dentine, 

 and consequently generally gets protection by a harder 

 tissue when exposed to hard work. 



The teeth of the Hake, used simply for piercing and 

 catching fish, are merely tipped with enamel (Fig. 86); 

 those of Ostracion, put to severer work, are coated with 

 enamel, while the teeth of the Wrasse (Labrus), which are 

 composed of ordinary dentine are, though very hard worked, 

 unprotected by enamel. 



Osteo-dentine. This is a tissue far more sharply marked 

 off from hard dentine, plici-dentine and vaso-dentine, than, 

 these are from one another, and approaches closely to bone, 

 from which it has few points of essential difference. 



The distinction can hardly be fully emphasized until the 

 development of dentine has been described, but it may be 

 mentioned that it is not developed on the surface of the pulp, 

 from an odontoblast layer, but within its whole substance. 

 Consequently in a completed osteo-dentine tooth there is no- 

 single simple pulp, which can be withdrawn from the 



