MASTICATION. 25 



germ or centre, similar to a granulation, into which ramify 

 numerous fine nerves and vessels (Fig. 11). This pulp, called 

 also the germ or bulb of the tooth, serves to form the tooth, 

 gradually becoming elongated and approaching the free edge 

 of the jaw, which it soon pierces, and so appears externally. 

 The portion thus denuded and exposed beyond the edge of the 

 jaw is called the corona of the tooth, whilst the portion called 

 n>etf remains imbedded in the jaw like a nail driven into a 

 board. The osseous cavity thus lodging the tooth is called 

 the alveolus, and the point of union of the corona and root is 

 called the neck of the tooth. When the dental bulb is fixed 

 to the bottom of its capsule by one or more pedicles, there 

 arrives a moment when the hard part of the tooth deposited 

 on the surface of the bulb surrounds it on all sides, compress- 

 ing its nourishing vessels so as to cause its obliteration. The 

 tooth ceases then to grow, the bulb wastes away, and a 

 central cavity alone indicates the place of this organ. But 

 when the bulb does not exhibit this arrangement, when it is 

 not pedunculated, and when the tooth forms only on the upper 

 surface, the growth of the tooth ceases not, and no central 

 cavity is found in its interior. 



c Fig. 11.* Fig.l2.t 



The large teeth found in the front of the mouth of the 

 rabbit (Fi<*. 10) offer an example of this kind of dentition ; 

 and if their length does not constantly increase, it is because 

 they are worn down by trituration on their cutting edge in 

 proportion as they grow at the base. 



* Section of a dental capsule, a, capsule; b, bulb or germ; c, blood- 

 vessels and nerves entering the germ; d, first rudiments of the ivory of the 

 tooth. 



t Lower jaw of a very young infant. The outer table of the jaw has been 

 removed to expose the capsules of the teeth enclosed in its interior, a, the 

 gum; b, lower edge of the jaw; c, angle of the jaw; d, dental capsules; e, 

 coronoid process; f, condyle of the jaw. 



