TEETH. 



293 



by no character more than by the singular 

 seeming exception which they present to the 

 Diphyodont rule which governs the dentition 

 of other hoofed quadrupeds. In fact, the 

 elephant, like the Dugong, sheds and replaces 

 vertically only its incisors, which are also two 

 in number, very long, and of constant growth, 

 forming tusks, with an analogous sexual dif- 

 erence in this respect in the female of the 

 Asiatic species. The molars, also, are suc- 

 cessively lost, are not vertical!}' replaced, and 

 are reduced finally to one on each side of 

 both jaws, which is larger than any of its pre- 

 decessors. These analogies are interesting 

 and suggestive in connection with the other 

 approximations in the " Sirenia" to the pa- 

 chydermal type, which I have pointed out in 

 the " Proceedings of the Zoological Society." * 



The dentition of the genus Elcphas, the sole 

 existing modification of the once numerous 

 and varied Proboscidian family, includes two 

 long tusks (fig. 592.), one in each of the 

 Intermaxillary bones, and large and complex 

 molars (ib. m. 3, 4, and 5) in both jaws : of 

 the latter there is never more than one wholly, 

 or two partially, in place and use on each 

 side at any given time; for, like the molars of 

 the Mastodons, the series is continually in 

 progress of formation and destruction, of 

 shedding and replacement ; and in the ele- 

 phants all the grinders succeed one another like 

 true molars horizontally, from behind forwards. 



The total number of teeth developed in the 



22 66 

 elephant appears to be i. ^^, m. Q^_'Q = 28. 



The two large permanent tusks being pre- 

 ceded by two small deciduous ones, and the 

 number of molar teeth which follow one 

 another on each side of both jaws being at 



" The socket of the pcnnane-.it tusk in 

 a new-born elephant, is a round cell about 

 three lines in diameter, situated on the inner 

 and posterior side of the aperture of the 

 temporary socket. The permanent tusks cut 

 the gum when about an inch in length, a 



Fig. 592. 



least six, of which the last three may, by 

 analogy, be regarded as answering to the true 

 molars of other Pachyderms. I have shown 

 in my Odontography that : 



" The deciduous tusk makes its appearance 

 beyond the gum between the fifth and seventh 

 month ; it rarely exceeds two inches in length, 

 and is about a third of an inch in diameter 

 at its thickest part, where it protrudes from 

 the socket ; the fang is solidified, and con- 

 tracts to its termination, which is commonly 

 a little bent, and is considerably absorbed by 

 the time the tooth is shed, which takes place 

 between the first and second year.f 



* 1838, p. 40. 



f See Mr. Corse's " Memoir on the Teeth of the 

 Elephant," in Philosophical Transactions, 17!9, 



211 : a good figure of the deciduous tusk is given 

 plate 5. 



Section of cfanmtn and tusk of the Elephant^ 



month or two, usually, after the milk-tusks are 

 shed. At this period, according to Mr. Corse *, 

 the permanent tusks are ' black and ragged at 

 the ends. When they become longer, and 

 project beyond the lip, they soon are worn 

 smooth by the motion and friction of the 

 trunk.' Their widely open base is fixed upon 

 a conical pulp, which, with the capsule sur- 

 rounding the base of the tusk and the socket, 

 continues to increase in size and depth, ob- 

 literating all vestiges of that of the deciduous 

 tusk, and finally extending its base close to 

 the nasal aperture (fig. 592.). The tusk is 

 formed by successive calcification of layers of 

 the pulp in contact with the inner surface of 

 the pulp cavity ; and, being subject to no 

 habitual attrition from an opposed tooth, but 

 being worn only by the occasional uses to 

 which it is applied, it arrives at an extraor- 

 dinary length, following the curve originally 



* Loc. cit., p. 212. 



