DEVELOPMENT OF THE ENAMEL 163 



in enamel which was not carious, but the subject of erosion, 

 the contours of the spherites being there also distinctly 

 visible, and he compared this appearance to that of the 

 interglobular spaces in dentine. 



These observations would appear to be strongly corrobora- 

 tive of the view held by Leon Williams and the author, 

 that the interprismatic substance of enamel is calcified 

 independently of the prisms, for it can be distinctly seen 

 that the small regular calcifying elements of the prisms are 

 quite distinct from these large calcospherites both during 

 development and in the completed enamel. 



Von Ebner does not hold with the view of Leon Williams 

 and Andrews that the prisms are calcified independently of 

 the interprismatic substance. He considers that each 

 ameloblast is provided with a separate Tomes' process, 

 which deeper in the first -formed enamel forms a separate 

 enamel prism, and that all the enamel cells together form 

 an interprismatic substance, in which the young prisms lie, 

 and by which they are surrounded. The prisms he considers 

 increase in thickness at the cost of the interprismatic 

 material, and in quite homogeneous enamel are completely 

 calcified. 



He also states that thin layers of uncalcified cement sub- 

 stance extend to the free surface of the enamel, where they 

 become continuous with Nasmyth's membrane. 



With regard to the existence of laminae in formed enamel, 

 which are arranged longitudinally between the dentine and 

 the surface, evidence is afforded by sections of human teeth 

 which have been treated with alcoholic fuchsin by capillary 

 attraction. The stain is seen to have spread over the 

 ground surface of the section in places, and if a section is 

 examined during the process of grinding it is seen that these 

 stained laminae are gradually ground away, portions of them 

 often remaining in the finished section. The staining of 

 these areas was long ago pointed out by Mr. Douglas 

 Caush (6), and corroborates the evidence afforded by the 

 teased preparations of marsupial enamel, which as pointed 

 out previously break up into plates or sheets at right angles 

 to the surface. 



In the chapter on tubular enamel the reasons are given, 



M 2 



