y///: 



A portion of the tooth is buried and solidly implanted in one of the 

 alveolar cavities of the maxillary bones; this is the /./ or iml>l<l1 y//7/. 

 (r/'//./K The other portion, circumscribed at its base by the gum, leaves 

 ilveolus to project into the interior of the mouth, forming the crown 

 or /;/< i>i,riit,n. The narrow constriction between the crown and root is named 

 the nadt 



The /<//;/ is perforated at its inferior extremity by one or more excavations 

 (I'liritii* IHI/IKI') which penetrate deeply into the substance of the tooth, and 

 admit into their interior the vasculo-uervous papilla, simple or ramified, 

 known by the name of the bulb or dental pulp. 



The i-i-"irn, the portion submitted to friction during mastication and, 

 consequently, to wear, offers the most varied forms : sometimes it is shaped 

 like a very acute cone; at others, it is divided into several tubercles more 

 or less salient ; and sometimes, again, it carries at the extremity of the tooth 

 a wearing surface more or less plane and regular. 



STBUCTURE. Three essentially different substances enter into the structure 

 of all the teeth : the /'<>///, enamel, and cement; to which ought to be added 

 :t parts, the pulp, j/""<, and alveolo-dentaJ periosteum. 



IVORY. The //.///. or </'';///<. has the hardness of bone, is of a whitish- 

 yellow colour, and is rendered brilliant in places by its nacrous reflection. It 

 forms the principal mass of the tooth, enveloping everywhere the pulp cavity. 



Examined by aid of the microscope, this substance is found to be 

 chiMineled by a multitude of minute, undulating, and branching canals 

 '(/ tiilmli i imbedded in amorphous matter the fundamental substance. 



Fig. 153. 



SECTION I II Kiin. II Illl 1 \Xi OF A MOLAR TOOTH. 



l>entine travcr.-c-il l.y its tubuli; ', '/, luterglobular, or nodular i 

 . . ' '1111111. 



The tiilmli. or niiKtliculi, extend from the dental cavity to tho inner face 



of the enamel : single at their origin, they Boon bifurcate, and again anasto- 



several times ilurin^ their slightly-undulating course. They terminate 



in a riil-ili'-xii,-, or in irri-^nlar cavities situated beneath the enanu 1. and 



named the interglobvlar HJHIWH <>f Ctemak (forming the mterohfailtr or 



'>/ /'///// i. These canals have a thin proper wall, and contain a dental 



fibre, which very probably is a continuation of the pulp-cells. The 



'.i/ Kiil.fttinr,- (or mnlr'i.,-\ is amorphous, and not very abundant ; in 



