in. LONG-NOSE, LONG-NECK, AND STUMPY. 45 



before me as I write, and which weighs nearly six pounds, 

 there are seventeen such ridges. But the hinder part of 

 the tooth had not cut the gum, and the last seven ridges 

 have not undergone any attrition. The ridges are com- 

 posed of hard enamel, the shallow valley along its summit 

 disclosing the softer dentine which lies beneath the fold 

 of enamel. Between the folds of enamel-coated dentine is 

 a much softer substance, called cement, by which the folds 

 are bound together. Since the cement and the dentine 

 are much softer than the enamel, they are more readily 

 worn away, and the tooth always preserves its ridgy, 

 grinding surface. 



The accompanying figures, one of which shows the 

 appearance of a tooth as seen from above, while the other 



ELEPHANT'S TOOTH FROM ABOVE. 



shows a diagrammatic section of a tooth cut in half along 

 its length, will, I hope, enable you to understand how 

 this most elaborate but most efficient grinding surface is 

 produced by the folding of the substance of the tooth 

 into a number of parallel ridges, and by filling up the 

 interspaces between the ridges with cement. In the 

 Indian elephant the foldings are much deeper and much 

 closer than in his African cousin. 



