256 MICROSCOPIC ANATOMY OF THE TEETH 



While we may look upon plicidentine as orthodentine in 

 which the arrangement of the tubes is so modified as to 

 produce a number of different and complicated patterns, 

 the next variety of dentine which we shall consider has an 

 altogether different structure. 



Vasodentine. Vasodentine differs from orthodentine 

 mainly in the fact that it contains no dentinal tubes, but 

 their place is taken by a system of blood channels containing 

 blood-vessels in connexion with the vessels of the tooth- 

 pulp. These blood-vessels have a very definite and regular 

 arrangement in typical vasodentines, blood corpuscles are 

 seen within them, and the blood in life circulates through 

 them. 



' The arrangement of the vascular canals is regular and 

 striking, , reminding one of the appearance of the vessels 

 in an intestinal villus ; in fact, an intestinal villus petrified, 

 whilst its capillary network remained pervious, and red 

 blood continued to circulate through it, would form no 

 bad representation of a typical vasodentine tooth.' 1 



Perhaps the most typical vasodentine is seen in the tooth 

 of the Hake (Merluccius) (fig. 159 and Plate VI). 



A strongly-marked lamination of the matrix parallel to the 

 surface of the pulp cavity is very evident in these teeth, and 

 that this is a structural condition is shown by the breaking 

 up of sections of the Hake's tooth into parallel laminae. 

 Thorn-like projections from the vascular tubes along the 

 lines of the laminse are also evident in many places (fig. 159). 



The outer layer of the tooth in the Hake contains no 

 blood channels and shows a faint indication of lamination. 

 This layer is described by Rose as vitrodentine, but as this 

 part of the dentine does not differ in structure or develop- 

 ment from the matrix material which intervenes between 

 the vascular tubes, Tomes does not consider that a distinctive 

 name should be applied to it. 



The vascular canals which do not enter this layer form 

 loops at its inner boundary which sometimes communicate 

 with a single peripheral channel in this situation (fig. 181). 



In the flounder, at and near the tip of the conical tooth, the 

 dentine is of the true orthodentine variety ; but lower down 

 1 C. S. Tomes, Dental Anatomy, 7th ed., p. 91. 



