208 PHILOSOPHY OF ZOOLOGY. 



The examination of the teeth of two individuals of the 

 common porpess, before I had perused the preceding ob- 

 servations of HUNTER, had induced me to adopt a diffe- 

 rent opinion with regard to the growth of the jaw, and to 

 conclude, that it enlarges at the symphysis as well as at 

 the base. In one of the individuals, which was only about 

 three feet in length, there were twenty-five teeth apparent, 

 and one before and another behind, underneath the sur- 

 face of the gum, in each side of the upper jaw, and twenty- 

 four in the under, and one not come through the gum in 

 front. In the other specimen, which was a pregnant fe- 

 male, five feet three inches in length, there were on the one 

 side of the upper jaw twenty-three perfect, and two uncut 

 ones in front, and on the other side, twenty-six perfect, and 

 three imperfect ones before. In the lower jaw there were 

 twenty-one perfect, and three imperfect ones on the one 

 side, and nineteen perfect and four imperfect ones on the 

 other, There are two incisors in the intermaxillary bones. 

 In these examples, the uncut teeth at the symphysis, ex- 

 actly resembled the uncut teeth at the base of the jaw. and 

 like them, were much smaller than those towards the mid- 

 dle. Indeed, when we view the shallowness of the groove 

 containing the sockets of the teeth at both ends of the jaw, 

 and the diminished size of the teeth, together with the 

 depth of the alveolar groove and the greater size of the 

 teeth in the middle of the jaw, there is sufficient reason to 

 conclude, that the first formed teeth are those in the mid- 

 dle of the jaw, that the jaw lengthens at the symphysis and 

 at the base, and that the new leeth formed at these places 

 are the smallest, and that there is no absorption. Those 

 teeth which have not cut the gum in the fore part of the 

 jaw, are every way analogous to the uncut ones at the base. 

 Tins lengthening of the jaw gives to the aged individuals 

 a more produced snout. Some observers have stated, that 



