312 Osteohglcal Description of the 



The head of the two-horned rhinoceros in our museum 

 exhibits indeed onlv twenty, apparently on account of the 

 age of the individual to which it belonged : but anatomists 

 are not deceived in these cases, because they know how to 

 find in the cello at the bottom of the jaw-bone, the germs 

 of the teeth which have not yet appeared ; and these germs 

 have really existed in this head, which would have had 

 twcnty-eitiht teeth, like all those of its species^ had not the 

 animal been killed too young. 



The skeleton of the one -horned rhinoceros, which forms 

 the principal part of the present description, exhibits also, 

 it is true, on one side of the lower jaw six teeth or stumps 

 of teeth, and on the other seven ; but this is only an ap- 

 pearance which cannot deceive when one has studied the 

 laws of the growth of teeth, especially according to the 

 method of Tenon. 



All herbiv^orous animals, beginning with the horse, wear 

 their teeth to the very roots, because, in proportion as the 

 crown is diminished by trituration, the alveolus fills up and 

 pushes the tooth outwards. When this root is composed of 

 two branches, as in the rhinoceros, and the shank of the 

 tooth is completely worn, there remain two stumps of the 

 root : these stumps dro)) out one after the other, always 

 lessened bv trituration and pushed outwards by the increase 

 of the bone in the interior of the alveolus. At length, 

 however, the alveoli themselves become entirely effaced. 



This is what in part took place in the rhinoceros in ques- 

 tion. It had already lost its two molar teeth, and the al- 

 veoli were almost entirely effaced ; the detrition of the two 

 following ones had been extended to the roots, and it had 

 even lost on one side one of the stumps of the roots, while 

 those of the other side both remained. 



Besides, no animal has nor can have an odd number of 

 teeth, considering the symmetry of the sides of the head, 

 and the suture which dividing the maxillary bones prevents 

 them from having an alveolus in the middle. Thus, when 

 one tooth more is found in the one side than in the other, 

 one is added in imagination to the latter. 



But if this rhinoceros had lost its molar teeth by age, it 

 had not gained incisors. This is not the case with it, nor 

 with other animals which grow old. The two small inter- 

 mediate incisors of the lower jaw exist at a young age, as 

 is seen by the head given to the cabinet of M. Adrian 

 Camper; and still better by the end of the lower jaw of 

 a very young subject drawn by his father, and inserted in 

 the Transactions of thcln)perial Academy of Sciences at 



St. 



