O T. C. WHITE OX THE SO-CALLED " NERVE OF THE TOOTH. 



be picked up by diligent and careful, but above all sf/ste/natic 

 observers. 



I trust that you will deal leniently with me if I presume for a 

 moment that you know nothing whatever of the various structures 

 entering into the formation of a tooth. I can thus, in an elemen- 

 tary manner, recall to your minds the osseous elements we meet 

 with in our examination. If a tooth be divided longitudinally the 

 main body of such a section would reveal three different substances 

 surrounding a cavity, which, to a certain extent, partakes of the 

 external shape of the tooth ; immediately surrounding the cavity, 

 and constituting the principal bulk of the tooth, we notice a fibrous 

 silky substance, called the " dentine ;" capping that part of the 

 dentine which appears above the gum, we see the crystalline, almost 

 msensible '^ enamel,^^ designed to protect the highly organised and 

 exceedingly sensitive dentine beneath it ; we shall also observe that 

 the dentine inserted in the jaw, and forming the root of the tooth, 

 is clothed with a material of a different appearance to the other two 

 substances — that is called the " cementumJ^ Of the enamel and 

 cementum, it is not necessary on this occasion to speak, but the im- 

 portant relation existing between the '' nerve " and the dentine 

 demands that I should enter more into detail in explaining its 

 microscopical appearance. In looking at a section of dentine under 

 the microscope in a well-developed human tooth, one is reminded of 

 those views of the comparative sizes of the rivers of the world given 

 in some atlases, only here our rivers are all the same diameter 

 and about the same length, and run together in parallel waves. If, 

 for the sake of illustration, we speak of them as rivers, we should 

 say that they arise beneath the enamel by exceedingly fine tribu- 

 taries, by the confluence of which the main stream is gradually 

 enlarged till, flowing on towards the centre of the tooth, its '^ de- 

 bouchure " helps to make up the walls of the central cavity, which is 

 occupied in the living state by the so-called " nerve." A closer 

 examination of our metaphorical rivers with higher magnifying 

 powers will show us that they are tapering and undulating tubes, 

 and existing so abundantly in the dentine as to impart to it that 

 fibrous silky aspect which cannot fail to strike the most casual 

 observer. These tubes, which, on the walls of the cavity, measure 

 about x-o-^Tjiyth of an inch in diameter, are occupied in a recent tooth 

 by transparent structureless fibres known as the dentinal fibrillge, 

 the exact office of which is but obscurely defined, but they may 



