490 ORGANS OF DIGESTION. 



monstrating it, is, to chip off the alveolus in front of a cuspate 

 to@th of the lower jaw, then seize the body of the tooth with a 

 pair of strong pliers, and make it rotate on its axis, the fibres 

 will thus be seen to start up and to show the attachment of their 

 two ends, one to the alveolus and the other to the tooth. The 

 jaw of a strong muscular subject is especially recommended. 

 This arrangement of the course of the fibres is very well exhi- 

 bited in the cow and horse. 



In the lower jaw of the adult, there is but one arterial trunk, 

 which supplies the teeth; but, in the fo6tus, and till the age of 

 six or seven years, there are two arteries,* and as many canals 

 for containing them. The lowest of these arteries belongs, 

 exclusively, to the deciduous teeth; it is distinctly visible in the 

 foetus, augments till the third or fourth year, afterwards it 

 shrinks, and is obliterated about the sixth or seventh year. In 

 some rare cases its canal remains open for a longer time, as 

 M. Serres has met with it in a woman of thirty. Being a branch 

 from the inferior maxillary, it enters the bone at a foramen 

 somewhat lower down than the posterior maxillary; and what 

 remains of it after the teeth are supplied comes out at another 

 aperture, a little below the anterior maxillary foramen, and 

 there anastomoses with the other dental artery. 



M. Serres supposes that this artery, discovered by himself, 

 and obviously serving in the evolution of the deciduous teeth, 

 by being obliterated before they fall out, destroys their vitality, 

 and, therefore, they become absolutely foreign bodies, the ex- 

 pulsion of which is required by nature on common principles. 



SECT. VI. OF IRREGULARITIES IN DENTITION. 



^ 



The process in certain individuals is premature; Louis XIV 

 was born with two teeth; many instances of the same sort o 

 precosity are recorded by Haller, and other medical writers, in 

 some of which even ten teeth were found protruded at birth. 



On other occasions, the process is retarded in a manner equal- 

 ly striking, and varying from the tenth month to the sixth or 

 seventh year. This unusual tardiness is sometimes manifested 

 in particular teeth; thus, I know a young gentleman in whom 

 * Serres, loc. cit. p. 17, 



