INTRODUCTION. Ill 



' tooth-substance' in the elephant's tusk, to which it is restricted 

 in common language and in the best zoological works. (1) I propose 

 to call the substance which forms the main part of all teeth ' den- 

 tine.'(2) 



The second tissue, which is the most exterior in situation, is the 

 * cement' (3). 



The third tissue, which, when present, is situated between the 

 dentine and cement is the ' enamel' (4). 



' Dentine' consists of an organized animal basis disposed in the 

 form of extremely minute tubes and cells, and of earthy particles : 

 these particles have a two-fold arrangement, being either blended 

 with the animal matter of the interspaces and parietes of the tubes 

 and cells, or contained in a minutely and irregularly granular state 

 in their cavities. 



The density of the dentine arises principally from the propor- 

 tion of earth in the first of these slates of combination ; the tubes and 

 cells contain, besides the granular earth, a colourless fluid, probably 

 transuded ' plasma' or ' liquor sanguinis,' and thus relate not only 



U) The accurate lUiger distinguishes the 'substantia ossea ' of a tooth from ' ebur,' and 

 separately defines both these modifications of the tooth substance. Prodromns Systemads Mam- 

 malium, 8vo. 1811, p. 20. 



(2) Dentinum. — Besides the advantage of a substantive name for an unquestionably distinct 

 tissue under all its modifications in the animal kingdom, the term ' dentine' may be inflected 

 adjectively, and the properties of this tissue be described without the necessity of periphrasis; 

 thus we may speak of the ' dentinal' pulp, ' dentinal' tubes or cells, as distinct from the 

 corresponding properties of the other constituents of a tooth. The term * dental' will retain 

 its ordinary sense, as relating to the entire tooth or system of teeth. 



(3) Ccernenium, Cortex osseus, Tenon. Crusta petrosa, Blake. 



(4) Encaustum, Adamas, Substaniia vitrea. 



a 2 



