Memoir upon living and fossil Elephants. ,365 



because ibe internal lamina of the capsule, which has alone 

 the power to secrete these two substances, does not extend 

 so far. 



1 am of opinion that it is partly to this absence of enamel 

 that the corrosion is owinc, which begins upon the roots as 

 soon as the portion of the corona corresponding to them is 

 worn down their lentrth. 



At this period the root has assumed all the development 

 of which it is capable ; the pulpy nucleus is entirely repelled 

 by the layers with which it has itself filled the cavity it oc- 

 cupied. This force of increasing of the root ceases there- 

 fore to counterbalance the increase of the osseous partitions 

 of the alveolus, and the latter continually push the root out- 

 wards. It begins to rot as soon as, when showing itself 

 out of the gum, it is exposed to the septic action of the air, 

 the heal and humidity of the mouth. 



What, in my opinion, adds some probability to this idea 

 is, that the corrosion begins rather at the junction of the 

 root and the corona than at the point of the root. I have 

 several proofs of this in my specimens. We may also judge 

 of it from the small tooth represented by Mr. Cjrse. (Phil. 

 Trans. 1799, PI. VL fig. 3.) Perhaps also tiie mechanical 

 compression uhich the root experiences froui the alveolus 

 contributes to its destruction, as we attribute the destruc- 

 tion of Tlie roots of the young teeth to the compression they 

 receive by the shrinking of their alveolus, occasioned by the 

 development of the teeth which must succeed ihcm. 



To conclude, one part of their molecules must be organi- 

 cally absorbed; but this would not be the only phainome- 

 non in which a body, become foreion, is sucked up by the 

 lymphatics, and disappears. The fact is known with re- 

 spect to liquids. As for solids, I think wc hav£ exam]>Ies 

 of it in some remote instances. We mav consult on this 

 head the dissertation by Alexander Macdonaid. 



The teeth of the two jaws of the elephant are easily di- 

 stinguished by their form. Those of the upper jaw have 

 their laminae disposed in such a manner, that ail their sum- 

 iijits are in a convex surface. The tablet produced by thf;ir 



detrition 



