FORMATION OF THE ENAMEL. 253 



The pulp elongates, sending off processes to form the 

 roots, which, in their descent, continue to deposit the ivory 

 around them. During this process, previous to the com- 

 pletion of the outer shell, we have the preparation for the 

 formation of the enamel. 



FORMATION OF THE ENAMEL. 



A diversity of opinion is entertained as to the manner in 

 which the enamel is formed. The doctrine most prevalent 

 at one period, was that the inner membrane of the dental 

 sac made a deposition of the enamel fluid, which by a pro- 

 cess of condensation resembling crystallization, ultimately 

 attained the extreme hardness and beautiful polish char- 

 acteristic of enamel. 



The most recent observations, however, seem to prove 

 that there is an especial apparatus provided for this pur- 

 pose, called by Raschkow, the adamantine organ and by 

 G-oodsir, the granular substance, which is described as being 

 within the dental sac, and becoming gradually absorbed ; 

 and that when the ivory is complete, the interior of this 

 sac is observed to present a " villous and vascular appear- 

 ance," having a thin layer of this granular substance upon 

 it, which layer is regarded as the enamel organ or membrane, 

 the matrix by which the enamel is furnished. 



Professor Harris also embraces this view from dissecting 

 the alveoli of a pig, and afterwards those of a " human 

 foetus at the fourth month/' where he, for the first time, 

 saw this granular substance, and was convinced that its 

 office was the furnishing the enamel, and that his previous 

 views were incorrect.* 



The microscope of Mr. Nasmyth demonstrates that the 

 enamel, as well as the ivory, consists of cells, and that it 

 is by the calcifying of these cells that the enamel is formed, 

 the deposit being first made on the prominences of the 

 tooth, then over the surface of the crown and body, down 

 to the neck, where it ceases. 



* See Harris's Principles and Practice of Dental Surgery. 



