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MANUAL OF ZOOLOGY. 



In both the living Elephants the " tusks " are formed by an 

 enormous development of the two upper incisors. The milk- 

 tusks are shed early, and never attain any very great size. The 

 permanent tusks grow throughout the life of the animal, and 

 often reach six or seven feet in length, and from fifty to seventy 

 pounds in weight, or even up to one hundred and fifty pounds 

 in aged males. In the Indian Elephant, and its variety the 

 Ceylon Elephant, the males alone have well-developed tusks, 

 but both sexes have tusks in the African species, those of the 

 males being the largest. The lower incisors are absent, and 

 there are no other teeth in the jaws except the large molars, 



Fig. 418. A, Left ramus of lower jaw of Elephas Indicus, viewed from above (after 

 Cuvier). B, Grinding-surface of molar tooth of Elephas Africamts (after Giebel). 



which are of very large size, and are composed of transverse 

 plates of enamel, surrounding tracts of dentine, and bound 

 together by cement. As the tooth wears down, the enamel 

 plates come to project, enclosing islands of dentine, which are 

 narrow and elongated in the Indian Elephant (fig. 418, A), but 

 are lozenge-shaped in the African Elephant (fig. 418, B). In 

 reality, there are six molars on each side of each jaw, but 

 owing to their large size, and the manner in which they succeed 

 each other, there is never more than one (or part of two) in 

 use on each side of each jaw at one time. The first three 

 teeth of the grinder - series, which would ordinarily be sup- 

 posed to be prsemolars, are in reality true molars, as they 

 have no predecessors or successors. None of the molars, in 

 fact, undergo vertical displacement, but the whole series 

 gradually moves forward in the jaw, and the place of each 

 tooth as it slowly advances is taken by the tooth next behind 

 it in the series, each succeeding tooth being usually larger than 

 its predecessor, and having more numerous plates of enamel. 



