80 On the Distribution of the Nerves of the Dental Pulp. 



the tooth, but become more and more scattered as tbey approach the apex 

 of the root. This is especially well shown by Ramon y Cajal's silver nitrate 

 process. The most successful preparations have been those prepared with 

 silver nitrate and with gold chloride, but the erratic manner in which these 

 substances select the tissues is well known, and it is only here and there 

 among some hundreds of sections that a thoroughly successful impregnation 

 is found. 



In this investigation I have made use of fresh calcified teeth ground on a 

 lathe, of teeth decalcified with nitric acid, and with formic acid, and of 

 calcified teeth ground on a stone after impregnation with balsam by the Weil 

 process. This latter method appears to me superior to all others, although a 

 very tedious and troublesome one to carry out successfully ; good preparations 

 fully repay the trouble ; there appears to be no shrinking of the cells, such as 

 occurs in specimens decalcified with acids, and the matrix of the dentine is 

 not stained. The staining of the matrix in decalcified specimens greatly 

 interferes with the clear observation of the contents of the tubules, the 

 minute longitudinal striation seen in the matrix, especially in silver prepara- 

 tions, giving rise to very deceptive appearances. In a well impregnated 

 balsam preparation the contents of the tubules are stained with the silver^ 

 the surrounding matrix remaining quite clear and unstained. 



I have also procured some very successful slides by staining a small piece 

 of a calcified tooth in bulk with a nuclear stain, passing it through the nitrate 

 of silver process, and then decalcifying with formic acid. 



In the substance of the dentine in well impregnated preparations fine 

 beaded fibres can be traced in the tubules, and in the majority of cases there 

 appear to be two fibres in each tubule which can be traced in many pre- 

 parations to the inner margins of the enamel and cementum. 



