92 MICROSCOPIC ANATOMY OF THE TEETH 



layer of dense enamel (fig. 44, c), which would suggest that 

 this layer bordering the dentine had been calcified previously 

 to the calcification of the main bulk of the tissue. A study 

 of the development of the enamel in these fish probably 

 gives the true explanation of this appearance. As shown 

 elsewhere (p. 186), the part near the dentine appears to be 

 laid down under the influence of true ameloblasts ; after 

 its formation the ameloblasts disappear as such and the 

 remainder of the enamel is deposited by a structure which 

 has assumed the form of a vascular secreting organ. 



FIG. 46. Sargus noct. Granules in tubes of enamel 

 of unerupted tooth. ( X 250. ) 



In many sections of these unerupted teeth of Sargus the 

 tubes are seen to be closely packed with small dark granules 

 which do not take the stain and which would appear to be 

 the calcifying substance conveyed to the enamel (fig. 46). 

 The principal points brought out by this investigation are : 



1. That the enamel of Sargus and many other fish which 

 show this outer striation is penetrated by tubes into which 

 a stain freely passes, their tubular nature being still further 

 evidenced by the presence of 'small granules which are seen 

 not only at the circumference but also deeply in the enamel 

 near their terminations. 



