( 1^5 ) 



tubuli which lie near the oiitfide of tlie tooth, (as far as they are- 

 above the gums, and expofed to the air) are extremely hard, being 

 as it were the folid cafe, ihell, or covering of the tooth ; and if we 

 examine the furface of this cafe or covering attentively, we fliall find 

 one tooth to have forty, another perhaps fifty circles on it, like wrin- 

 kles, or gatherings, which in fome places run in a curved or wavy 

 dire6lion, as is reprefented in the figure at D E F, where a drawing 

 is given of this outfide fhell, with fome of the circles marked there- 

 on ; and I imagine that the circles which thus appear like wrinkles 

 proceed from hence, that tiiey are the places where the tooth, while 

 growing, is from time to time protruded or thruft out from the gum. 



In the teeth fhed by children, and likewife in thofe of many young 

 animals, I have obferved that the ends of their roots are entirely 

 open or hollow ; and in like manner I imagine that the roots of the 

 molar teeth or grinders which I have been juft defcribing, are at 

 firft formed in the fame manner, but that in procefs of time tliev 

 become oflified or converted into a boney fubftance, of a fpongy 

 nature, through which many vefiels pafs, conveying blood, and nutri- 

 tive juices into the cavity of the tooth, and I alfo conceive that this 

 cavity is filled with nerves and vefTels fpreading themfelves into fo 

 many branches, that every one of the boney tubuli is thereby in- 

 creafed during the time of its growth, and afterwards, (while the 

 tooth continues found) nouriflied and fupported. 1 alfo conjedlure 

 that thefe fmall vefTels thus nourifhing and fupporting the boney 

 tubuli do not end at the furface of the tooth (I mean, in that part of it 

 which is within the gum ) but that the aliment or nutritive lubftance 

 has a continued courfe through thefe vefTels , and that the ends of the 

 boney tubuli are again converted into fofr or pliable veflels, fpread- 

 ing through the gum, and that thofe veflels are what principally keep 

 the tooth fixed in its place. 



The firfl formation, and fubfequent fupport or nourifhment of the 



