

DEVELOPMENT OF THE TEETH. 485 



the direction of their length may be admitted to occur (see 

 fig. 103, 2). The jelly of the enamel organ (enamel pulp) 

 possesses only a transitory and mechanical significance, occupy- 

 ing the space subsequently required by the growing tooth, 

 Nevertheless, before the formation of the enamel is completed, 

 both the epithelial and gelatinous tissue and the stratum inter- 

 medium undergo atrophy. The outer and inner epithelia 

 consequently again come into close apposition (see fig. 102) ; 

 the latter is entirely used up in the formation of the enamel, 

 and in teeth examined just at the period of eruption we can 

 only detach from the enamel a membrane composed of one or 

 more layers of very flat epithelial cells, which clearly represent 

 the outer epithelium with a larger or smaller amount of the 

 stratum intermedium. As soon as the eruption of the tooth is 

 effected, these cells become horny, and form the cuticula dentis. 



This conversion so remarkable in a histological point of view, of a 

 portion of the epithelial cells of the enamel organ into stellate 

 gelatinous tissue, finds an analogy, according to Kolliker (58), only in 

 the cells of the external investment of the egg of the Perch. I have 

 myself occasionally met with a similar metamorphosis of the epithelial 

 cells in the Graffian follicles, but never occurring in so regular a 

 manner. Kenewed investigations, notwithstanding the objections 

 raised by Kolliker (58) and Kollmann (67 a), compel me to adhere to 

 the view I have above expressed of the nature of the cuticula dentis. 

 Its tenuity cannot be considered as an objection, especially if, as I am 

 now inclined to believe with Hertz (52), the external epithelium is 

 alone to be regarded as the basis of the cuticula. 



The formation of the enamel is purely and exclusively refer- 

 rible to the enamel epithelium, the enamel prisms resulting 

 from the direct calcification of the long cylindrical cells. The 

 intimate connection of enamel cells with small portions of the 

 enamel prisms, which remain adherent to the cells in the form 

 of processes, is in the first place in favour of this view (see fig. 

 103, 3). Again, the limit to which the calcification extends is not 

 bounded by a straight line, but is very irregular, a circumstance 

 that is opposed to the idea of a calcification of any secretion 

 formed by the enamel cells. If young enamel be treated with 

 diluted acids, the enamel prisms swell up to some extent, and 



