THE DENTAL PULP 



233 



Walrus, and in many marsupials as in the lower incisors 

 of the Kangaroo the procumbent incisors of the Hypsi- 

 prymninae, and both the incisors and molars of the rodent- 

 like Wombat. In the Wombat also a layer of cement 

 is continued over the surface of the incisors covering the 

 enamel, while in Rodents the cement is not continued 

 over the surface of the enamel. In these scalpriform incisors 

 a sharp edge of enamel is maintained by the unequal wear 

 of the tissues of the tooth, the dentine and cement wearing 



FIG. 142. Spear-head embedded in tusk of Elephant. 



down much more quickly than the hard enamel which 

 projects as a sharp cutting edge. 



In the fish, the rostral teeth of the Saw-fish (Pristis) grow 

 from persistent pulps, and they are also implanted in sockets. 



There are certain peculiarities in the shape and extent 

 of the pulp cavities in the teeth of ancient forms of man 

 recently discovered. 



In the Heidelberg mandible the pulp cavities are very 

 much larger in proportion to the hard tissues than in 

 modern man. Especially in the Krapina teeth, as shown in 

 Professor Keith's skiagrams, is this noticeable, the pulps 



