-274 



HIPPOPOTAMUS TEETH OR TUSKS. 



these tusks is to be attributed. It is the combination of these especial 

 qualities, density and whiteness, that makes the hippopotamus teeth, so 

 invaluable to the dentist. 



On the other hand, the absence, of oily matter, and the comparatively 

 smaller amount of animal substance in this bone, induces brittleness, and 

 causes it to be more easily affected by the acids of the food, and saliva. 



The enamel is still harder and whiter than the dentine, by reason of 

 its being composed almost exclusively of phosphate of lime, with only about 

 4 per cent, of organic matter. Dentists are the principal consumers of the 

 canines of the hippopotamus ; for no bony substance has hitherto been 

 found that possesses, to so great an extent, the properties requisite to the 

 successful performance of their art. Mineral teeth are, for the moment, in 

 great favour ; but, after all, it is very questionable if any artificial substance 

 can be made so appropriate, as the precise material which an Infinitely Wise 

 Being has selected, and supplied, both to man and the lower animals, for the 

 purpose of mastication. 



1. Lower end section of canine tusk of the upper jaw. 



2. Canine tusk of the lower jaw. 



3. Lateral incisor tusk of lower jaw, showing the extent of the hollow portion. 



"When these tusks are employed for the manufacture of front teeth, the 

 enamel on the surface is valued, and retained, for the sake of its delicate 

 whiteness and density, as before described ; and the tusk is so manipu- 

 lated that this enamel forms the outer or visible surface of the teeth. But 

 when used in the production of artificial guni, or back teeth (molars), the 



