( ii6 ) 



tooth being as before defcribed, we may eafily conceive that the 

 boney tubuli, (being of a folid nature, and incapable of dilatation or 

 fprcading) may happen to be obrtruited by fome grol's or concreted 

 matter, and then the fmall velTels contained within the cavity of the 

 tooth mufl: immediately by fuch obftru(^lion in the circulation of 

 their juices be dellined. This diftention or fwelling will necellarily 

 excite great pain, for all the vellels contained in the tooth will prefs 

 clofely on each other, foral'much as they cannot fwell or fpread 

 themfelves as other veflcls can, which are not confined within the 

 folid fubftance of a bone. Again, fuppofing thefe boney tubuli to be 

 obllru(51:cd, and the obflru61:ion not removed, we may from thence 

 gather the reaion why our teeth partially decay, fometimes on the 

 fides, and fometimes at the tops, the reft of the teeth remaining 

 found for feveral years after. 



In order to flievv the proportion which the fize or thicknefs of the 

 tooth bears to its component parts before defcribed, I placed a very 

 fmall piece of this tooth before the microfcope, and delivered tliat 

 microfcope to the limner, directing him to draw an exac^l reprefen- 

 tation of what he faw, (but without acquainting him what that objetfl 

 was). And here I muft obferve, that in this tooth the tubuli appear- 

 ed to me much larger than I had before obferved in any animal, or 

 in the elephant's tooth. 



In Plate V. at fig. 2, K L M N, is reprefented * an exceeding 

 fmall particle, or piece of a human tooth, of that fort called the 

 molar teeth, or grinders, as feen through the microfcope. The reafon 

 why in this figure fome of the tubuli there pictured appear of a 

 darker fhade than the reft, is only this, that in that place where 

 they feem darker there were more of the tubuli lying one 



* The author having jufl: below informed us, that 120 of the boney tubuli make only the 

 forty-fifth part of an inch, we may, by counting the tubuli reprefented in this figure, judge the 

 natural fizc of the fragment, or piece of tooth here magnified, and it will be found to be about 

 the fortieth part of an inch in Isngth and the fiftieth part of an inch in breadth, or of the fize 

 (hewn at X. 



