POISONOUS SERPENTS. 233 



There is, however, no trace of true enamel upon the teeth of the 

 poisonous serpents any more than upon those of the innocuous species. 

 The cells of the cement are more minute and inconspicuous in the 

 poison-fang, than in the simple teeth of the Python and Boa. 



The teeth of all Ophidians are developed and completed in the 

 original seat of the tooth-germs in all animals ; viz. the mucous 

 membrane or gum covering the alveolar border of the dentigerous 

 bones. This gum presents the same lax tissue and is as abundantly 

 developed as in the Pike, Lophius, and many other fishes, in which it 

 likewise serves as the nidus and locality for the complete development 

 of the teeth. 



The primitive dental papilla in the common harmless snake very 

 soon sinks into the substance of the gum and becomes inclosed by a 

 capsule. As soon as the deposition of the calcareous salts commences 

 in the apex of the papilla, the capsule covering that part becomes 

 ossified and adherent to the dentine, and the tooth begins to pierce 

 and emerge from the gum, before its mould, the pulp, is half com- 

 pleted. Fresh layers of cells are successively added to the base of 

 the pulp, and converted by their confluence and calcification into the 

 tubular dentine, until the full size of the tooth is attained, when its 

 situation in the gum is gradually changed and its base becomes 

 anchylosed to the shallow cavity of the alveolar surface of the 

 bone. 



In the posterior part of the large mucous sheath of the poison-fang, 

 the successors of this tooth are always to be found in different stages 

 of development ; the pulp is at first a simple papilla, and when it has 

 sunk into the gum the succeeding portion presents a depression along 

 its inferior surface, as it lies horizontally, with the apex directed 

 backwards ; the capsule adheres to this inflected surface of the 

 pulp. But how the cylindrical cavity of the dilated fold is occupied 

 in the loose growing poison-fang, and by what contrivance it is 



however, it passes over that sUt, it will cover it with enamel and in some cases by that means 

 alone the edges become soldered together."— Philos. Trans. 1818, p. 473. 



The author appears here to have been misled by the prevalent doctrines of dental develop- 

 ment ; no tissue of a tooth is deposited from a surface : a distinct convertible matrix or mould 

 is as essential to the formation of enamel, as of cement or dentine, and unless such organ be deve- 

 loped from the inner surface of the capsule, no enamel can be formed. 



