214* THE ANIMAL KINGDOM. 



which covers the ivory, and is extremely hard, brittle, and 

 fibrous. The fibres of enamel, separated by muriatic acid, 

 are found to be six-sided prisms, about l-6000th in breadth, 

 and transversely striped, which are well seen under the 

 polaricope. 



SECTION OF HUMAN TOOTH, 

 (Perpendicular,) 



will show the enamel on the crown, like a narrow border 

 running round ; the ivory in a broad band round the pulp- 

 cavity ; and the cement round the fang, dotted with lacunae. 



SECTION OF HUMAN TOOTH, 

 (Transverse,) 



will only show the enamel and the ivory. 



Tooth of Saw-fish. 

 Sperm Whale 



Jaw of Myliobates, or Eagle 

 Bay-fish. 



Wolf-fish. 

 Elephant's tooth. 

 Tusk of Sus Indicus. 



