200 ON TUE FOSSIL BONES OF rACHYDEBMATOUS QUADRUPEDS. 



we see that it is as it were gnawed ; it jDresents on its surface small 

 irregular fossetts, as if it had been dissolved by an acid thrown on it in 

 drops. It is a sort of caries similar to that which the teeth undergo 

 in man, when they are deprived of their enamel. We shall inquire 

 into the cause of this farther on. It always happens that the tooth is 

 thereby successively deprived, in the different portions of its length, 

 of segments or slices, which occupied its entire height. 



Hence again results another singular effect : it is this, that as the 

 anterior part of the jaw must be always lilled, the tooth moves from 

 behind forwards in the horizontal direction, at the same time that it is 

 carried in the vertical direction from above downwards, or from below 

 upvvards, according as it belongs to the upper or lower jaw. 



This is the reason why each tooth, at the time it falls, is found to be 

 very small, however large it may have been originally. 



This movement of the tooth now in action makes room for that 

 which is formed in the posterior jaw, and which is to succeed it; this 

 second tooth aids, by its development, in pushing the first forward ; 

 and we might say that the secondary teeth in the elephant come behind 

 its milk teeth, instead of coming above or below them as in other 

 animals. 



Patrick Blair*, who perceived separate transverse lamellse in the 

 back-jaws of the elephant, and who called them very properly rudi- 

 ments of teeth, was not disposed to believe that these lamellea came 

 afterwards to form a tooth which was to replace that behind which he 

 found them. He was then reduced to seek various imaginary uses of 

 them. 



The number of the teeth of elephants has been a subject of dispute ; 

 the Royal Society of London perceived, in 1715, that it varies from 

 one to two on each side, and that the place of the division varies also: 

 that is to say, that the first tooth is more or less long in proportion to 

 the second, according to the individualsf . 



Pallas was the first who taught the mode of their succession, which 

 explains all these irregularities, by showing that they have at first only 

 one tooth on each side ; that a second, in developing itself, pushes on 

 the first, so that for a certain time there are two of them ; then the 

 falling of the first causes them to be but one againj. 



I announced that this succession, and consequently this alternating 

 change of number, was repeated more than once, because I still found 

 separate germs in an elephant ^vhich had already two teeth. This lat- 

 ter point had in fact been already proved by Daubenton §, but for the 

 upper jaw only ; in fine, this great naturalist had perceived to a cer- 

 tain degree the necessity of this succession from behind forward, 

 which Pallas more clearly developed. 



M. Corse || apprized us that this succession is repeated as often as 

 eight times in the elephant of India ; that there is therefore thirty-two 

 teeth, which occupy successively the different parts of his jaws. 



The first appear eight or ten days after birth, are well formed in six 



* Phil. Trans, vol. xxvii, No. 326. f Phil. Trans, vol. xiix. 



X Nov. Com. Petrop., xiii, p. 475. § Hist. Nat. torn, xi, in 4to. 



\\ Phil. Trans* for 1799. 



