OF LIVING ELEPHANTS. 203 



disappear. The thing is well known for liquids. For solids, I think 

 that we have examples of it in some secretions. The essay of Alex- 

 ander Macdonald on Necrosis may be seen on this subject. 



The teeth of the two jaws of the elephant are easily distinguished 

 by their form. Those of the upper jaw have their lamellae so disposed 

 that the summits are all in a convex surface : the table produced by 

 their wearing is also convex. The contrary in both these points takes 

 place in those of the lower jaw. 



A character still more striking may be taken from the direction of the 

 lamellae with respect to the crown or triturating part. 



Those from below are inclined backward, that is to say, the acute 

 angle which they form with the plane of trituration is directed forward, 

 at least in their radical part ; for the summit of the anterior ones is 

 curved a little backwards. 



Those above, on the contrary, are inclined forwards, or the acute 

 angle which they form with the plane of trituration is directed back- 

 wards. 



It is always easy to distinguish the back of a tooth from the front : 

 trituration wearing away much more in front than posteriorly, it is 

 the end of the crown most deeply worn that is always anterior. 



It is necessary to remark, however, that the inclination of the lamellae 

 on the crown diminishes in the two jaws in proportion as the detrition 

 increases. The posterior lamellae, which are worn much later, are 

 worn a little more quicklj'-, because their development towards the 

 root continuing, when that of the anterior lamellae has ceased, they are - 

 pushed out with more force, whence it happens that the plane of de- 

 trition becomes more and more perpendicular to the direction of the 

 lamellae. 



The teeth belonging to each side may be still distinguished, because 

 they are convex on their internal surface, and a little concave on the 

 external. 



I endeavoured to represent this progress of dentition in the figures 

 of my plates 9 and 10. 



PL 10, Jig. 5, is a cranium of an elephant of India, cut vertically. 



a. The entrance of the nares. 



5, b. The enormous thickness of the sinuses, which separate the. 

 two parietes of the cranium. 



c. The cavity of the brain. 



d. The occipital foramen, and the right condyle of the same name. 



e. The alveolus of the tusk. 



/. The cavity of the tusk, opened to show the sj)ace occupied by its 

 pulpy nucleus. 



In the space from/ to ^r, a portion of the maxillary bone has been 

 removed, and all the palate bone, to shew the teeth, and their germs 

 in situ, in all their extent. 



h. Is the anterior tooth, reduced almost to nothing by detrition, and 

 the pressure as well of the next tooth, as of its own alveolus. 



i. The tooth in full activity, the roots of which begin to form at k, 

 and of which the triturating part I is already worn down. The pos- 

 terior lameUse m are still untouched. 



