98 CLASS MAMMALIA. 



or milk-teeth, and permanent teeth ; but whether the latter 

 have had predecessors in all cases is not ascertained, owing 

 to the very early period, if at all, at which the succession 

 takes place. 



The Baron has watched this operation of nature in the 

 hare ; the upper posterior incisors only were observed to 

 change; the cheek-teeth continuing a long time, with their 

 permanent successors, during which time the animal ap- 

 peared to have six incisors above, instead of four, the pro- 

 per number. 



Of the Molars it is certain that there are three out of six 

 in the upper jaw, and two out of five in the lower, which 

 change ; the three posterior cheek-teeth, on both sides in 

 each jaw, come but once, and in this respect the hares are 

 like the horses, and the ruminating animals ; the upper 

 surface of the posterior cheek-teeth accord with those which 

 succeed the anterior deciduous cheek-teeth. 



I rather think, says the Baron, that in the species which 

 have but four cheek-teeth on each side, there is but one, 

 the anterior, which is changed ; at least I am satisfied it is 

 so with the Castor, the Porcupine, the Agouti, the Paca, 

 and the Cavy ; but to examine the new tooth in this last 

 species when quite new and unused, the animal must be 

 taken very young ; and what is certainly very singular, in 

 order to see this cheek-tooth in its place, the animal must 

 be inspected some days before its birth. I have satisfied 

 myself that this tooth in the Cochon d'Inde, falls while 

 the foetus is still in utero ; and by analogy, I suspect that it 

 is the same with all theRodentia, as to their incisive teeth. 

 These, therefore, would no longer be milk-teeth, but uterine 

 teeth. 



In this instance it may be observed, and in many others 

 we may find, though less forcibly, an apparent unwilling- 

 ness in nature to depart from those general laws to which 

 she submits creation. We are not always able to detect 



