478 ORGANS OF DIGESTION. 



Iral pulp of the teeth is furnished with the latter. The teeth 

 are composed of two kinds of calcarious matter, one ivory-like, 

 the other enamel; the bones, on the contrary, have but one.* 

 To this we may add, that the teeth have no power of intersti- 

 tial growth like the bones. It is also said by naturalists, that 

 in mammiferous animals, the teeth present insensible transitions 

 from their most perfect state to a lamellated condition resem- 

 bling horns and nails.t Some animals, as the shark, have the 

 teeth only adhering to the gum and not fixed in sockets, others 

 have them in the stomach : both of which circumstances serve 

 to illustrate still farther the independence of the teeth upon the 

 osseous system; and that their being fixed in sockets belonging 

 to the latter, is merely a collateral and not an essential ar- 

 rangement. 



SECTION III. 



The Gums (Gingivce) are a continuation of the lining mem- 

 brane of the mouth over the alveolar processes, but its texture 

 there is much changed; as it becomes more fibrous and vascu- 

 lar, and loses much of its sensibility and capability of being ex- 

 tended. As the gums cover both the lingual and the buccal cir- 

 cumference of the alveolar processes, they adhere very closely 

 to the .periosteum, and send in partitions through the interstices 

 between the teeth. They also adhere tightly to the neck of 

 each tooth, so that when the latter is drawn, the gum, unless 

 previously detached, is apt to be lacerated; this adhesion is by 

 a sort of rounded or partially doubled edge, that admits of a 

 slight degree of motion, and which, from its thickness, if it be 

 removed by ulceration or by pressure, causes the tooth to ap- 

 pear to project unnaturally from its socket. The teeth, from 

 being united to the jaw by the gum, and by the periosteum 

 being continued over the cavity of the socket; have preserved 

 to them that degree of yielding motion which prevents them, 

 on their unexpected and forcible application to hard bodies, 

 from being fractured, and also saves their sockets.J 



* Serres, loc. cit. 



t Traducteurs de J. F. Meckel. 



$ J. Hunter, loc. cit. 



