THE MOLARS. 633 



is only a single cavity, very diverticulated, in the interior of which the dental 

 pulp is contained. 



It will be understood from this that the infundibula of the free extremity 

 correspond to two somewhat conical reflections which are situated one in front 

 of the other and surrounded, outwardly as well as inwardly, by the internal 

 cavity. 



Inferior Molars. — The development of the inferior molars is much more 

 simple. In fact, if the free extremity be first examined (Fig. 302, A), it is seen 



O I O 



Fig. 302.— Inferior left molar removed from its dental follicle. 



A. Viewed by its free extremity : 



a, anterior infundibulum. i e, external border of the infundibula. 



a', posterior infundibulum. I i, internal border of the infundibula. 



B. Viewed by its incased extremity : 



m, n, 0, pulp cavity. Other letters same as in A. 



that the infundibula, a and a'', are produced by two reflections of the enamel from 

 the internal face towards the centre of the tooth. They are also cleft outwardly 

 throughout their whole length. The cleft of the posterior infundibulum, a\ 

 occupies the middle part of this cavity, while that of the anterior, a, is situated 

 much more in front. An inferior left molar can thus at a glance be recognized 

 from its homologue of the right side. 



The mode of formation of the infundibula of the inferior molars is therefore 

 different from that of the superior. Both result from the penetration of the pa- 

 pillae, but, in the former, it is through one of its lateral faces that a longitudinal 

 papilla enters the tooth ; in the latter, on the contrary, a conical papilla enters 

 through the summit. 



Concerning the opposite extremity of the inferior molar (Fig. 302, B), there is 

 found a spacious cavity, m, n, o, very much diverticulated, surrounding the periph- 

 ery of the infundibula, a and a', isolating the one from the other, and separating 

 them from the external face, m, n. The three diverticula, m, n, o, of this cavity, 

 communicating with one another, lodge three prolongations of the internal pa- 

 pilla or the pulp ; all terminate in cul-de-sacs at the free extremity of the tooth, 



2. Structure. 



The molars, like the incisors, are composed of a flindamental substance and 

 two protecting envelopes. 



a. The enamel constitutes the only element in the tooth when the latter is 

 first developed. Having formed the four faces, it is reflected upon the free ex- 

 tremity (supericir molars) to circumscribe the infundibula. 



