XXIV INTRODUCTION. 



enamel the greatest departure is observable, but not 

 wider than its peculiar function suggests; and it must 

 be remembered, first, that it is the least constant tissue 

 of the teeth; secondly, that its chemical composition 

 is very much the same as that of the dentine and 

 cement, both of which resemble bone. Lastly, the 

 analogy is completed in a review of the mode of tooth 

 development. Thus, upon a mucous papilla a large 

 quantity of gelatinous matter is observable, in which 

 certain cells appear. The gelatinous matter resembles 

 the incipient cartilage in which ossification begins. 

 This papilla is supplied with an artery, which nour^ 

 ishes its cells, and the cells gradually so develop that 

 the older ones are pushed outward and form the 

 dentine." 



HOW MADDER AFFECTS THE TEETH. 



John Hunter, one of the most celebrated physiolo- 

 gists of the eighteenth century, made many experi- 

 ments on the teeth of different animals, one object 

 being to determine whether they were vascular or not. 

 His conclusion was that they were not vascular, and 

 he founded his belief partly upon the following experi- 

 ment ("The Human Teeth," pp. 23-4): 



" Take, for example, any young animal, as a pig, and 

 feed it with madder for three or four weeks; then kill 

 it. On examination you will find the following ap- 

 pearances : First, if the animal had some parts of its 

 teeth formed before the feeding with madder, they 

 will be known by their remaining of the natural color; 

 but such parts of the teeth as were formed while the 

 animal was taking the madder will be of a red color. 

 This shows that it is only those parts that were formed 

 while the animal was taking the madder that are dyed; 



