354 A MANUAL OF DENTAL ANATOMY. 



of the thousands of years which have gone by since their 

 possessors perished. 



The trade in ivory is quite an important one, the Board 

 of Trade returns for 1879, giving 9,414 cwts., of the value of 

 .406,927, as the quantity brought to this country. 



The best ivory is that which comes from equatorial 

 Africa; Indian ivory, is not so highly esteemed, and Mam- 

 moth ivory is so uncertain in its degree of preservation 

 that it does not find a ready sale, even though some samples 

 almost attain the quality of recent ivory. 



The last remains of the pulp are converted into dentine 

 in which a few vascular canals persist ; this of course occu- 

 pies the centre of the tusk, and is small in amount. 



Six molar teeth are developed on each side of the jaw by 

 the elephant, and, arguing from analogy, they are some- 



3 3 



times classified thus milk molars - true molars - ; 



3 3 



occasionally a rudimentary tooth in front brings up the 

 number to seven on each side. But the peculiarity of their 

 mode of succession renders such a classification merely 

 arbitrary, so far as the elephant itself is concerned, and it 

 depends upon analogy with the teeth of the mastodon. 

 Though the elephant has, during the course of its life, 

 twenty-four molars, they are not all in place, nor indeed 

 are they all actually in existence at the same time. Only 

 one whole tooth on each side, or portions of two (when the 

 front one of the two is nearly worn out), are in use at the 

 same time. After a tooth has been in use for some time, 

 and is worn down, a new tooth comes up to take its place 

 from behind it, and absorption in the old tooth being set up, 

 it is shed off, and the new tooth pushes forward into its 

 place (see fig. 151). Each successive tooth is of greater 

 size than its predecessor ; thus in the Indian elephant the 

 first tooth having, on an average, four transverse plates; 

 the second eight, the third twelve, the fourth twelve, the 



