480 ORGANS OF DIGESTION. 



ly to the neck of the latter and to its root. These sacs, or fol- 

 licles, as they are sometimes called, are visible in the tenth 

 week of uterine existence. 



The Pulp, or germ of the tooth (Pulpas Dentis) is a very 

 vascular body, and adheres to the socket only at its bottom, 

 where the vessels enter; it becomes sufficiently distinct about 

 the fourth month of foetal existence, and rises up then from the 

 base of the internal membrane of the sac like a small simple 

 tubercle. In developing itself it acquires the precise form pe- 

 culiar to each tooth, and is actually the mould for it: it is sur- 

 rounded by a very fine vascular web, which is detached from 

 it with much difficulty. 



The ossification of a tooth first commences on that surface 

 of the pulp next to the gum, by one or more points according 

 to the number of projections, which the future tooth is to have 

 on its grinding surface. The osseous deposite in its very early 

 stage is thin, soft, and elastic, but soon acquires a hard con- 

 sistence. The incisors begin to ossify by three points, the cus- 

 pidatus by one, the bicuspis by two, and the molaris by three, 

 four or five. The several points of ossification continue to in- 

 crease till their bases come into contact; they then coalesce, 

 and afterwards the tooth grows as an entire body. The tritu- 

 rating surface of the tooth being first formed after this manner, 

 a deposite of bone then takes place along its edges, till the 

 body of the tooth, with the cavity in the centre, is completely 

 built up. Jn this progress, it gradually surrounds the pulp, till 

 the whole of the latter, excepting its base, is covered with 

 bone. 



The adhesion of the pulp to the new-formed bone is such as 

 to require some slight force to separate them; but this may be 

 done without rupturing either the one or the other; their sur- 

 faces which were in contact are perfectly smooth, neither is 

 there any evidence of a vascular communication between 

 them.* The line of the strongest adhesion is along the latest 



* Hunter, Scrrcs, Mcckel, loc. cit. 



