DIFFERENCES IN HISTOLOGICAL STRUCTURE OF TEETH. 461 



fish is quite red, and that, the canals being of just the 

 size of the blood-vessels, they contained practically nothing 

 else. 



A typical vasodentine, therefore, consists of a matrix per- 

 meated by a rich plexus of blood-carrying channels, and contains 

 no dentinal tubes whatever of the ordinary kind; the matrix is 

 laminated, but is quite solid (4). 



It would, however, be out of place to recapitulate here all the 

 details which are, for the most part, to be found elsewhere, and 

 it will suffice to describe those points only which are relevant 

 to the title of the paper. 



The teeth of the ling (Molva) may be taken as typical of 

 that group in which the vascular system attains to its fullest 

 development ; they are long conical teeth, slightly curved and 

 very sharp, and have large axial pulp chambers which are 

 also elongated cones, and extend through the greater part of 

 the length of the teeth. 



From these pulp chambers the vascular canals run outwards, 

 almost at right angles to the surface in the lower part of the 

 teeth, whilst near to their apices they run obliquely upwards; 

 they are disposed with the utmost regularity, and anastomose 

 with one another to some extent. 



They do not reach to the surface of the dentine, but all 

 terminate in loops at exactly the same distance from the 

 surface, the loops in which they terminate being flattened, so 

 that the terminal canals lie parallel with the surface, and 

 there is an appearance of a bounding channel parallel to the 

 exterior of the tooth (figs. 1 — 3). 



This disposition of the vascular canals is equally charac- 

 teristic in the hake (Merlucius) ; in both fish the outer solid 

 layer of the dentine shows a faint striation parallel with its 

 surface, which appears to be due to slight lamination. 



The apex of the tooth is kept sharp by a little spear-point of 

 enamel, neatly fitted on to the dentine in such wise that it 

 does not much increase its size, although itself of material 

 thickness. This spear-point of enamel is possessed by all the 

 family, and does not show much distinct structure, though in 



