422 



MAMMALIAN ANATOMY 



variations. The following observations on the eruption of the teeth 

 in animals of known ages, although correct in themselves, may not 

 hold good for all specimens. 



At seven days after birth no teeth have appeared and none can be 

 distinctly felt through the gums. After the gums have been cut away 

 the upper incisors and canines can be seen in the alveolar border. 



At eleven days no teeth have come through the gums ; the first 

 and second upper incisors, however, can be plainly felt. After the 

 gums have been cut away the first and second upper incisors and the 

 points of the third incisor and of the canine protrude through the 

 bony alveolar border. 



At thirty days all the teeth, except the first upper molars, have- 

 appeared through the gums. There are then visible about one- third 

 of the upper canines and slightly more of the lower canines, one-half 

 of the first lower molar, the points of the upper sectprial, and one point 

 of the lower sectorial. After the gums have been cut away the teeth 

 are seen to be clearly through the alveolar border ; the small first 

 upper molar is just appearing. 



FIG. 344. 



ERUPTION OF PERMANENT FIRST UPPER INCISOR 

 TOOTH. 



At forty-four days the teeth protrude much further ; the first upper 

 molar is, however, still hardly apparent. 



At sixty days the deciduous dentition is complete. 



I have not been able to fix precisely the date of the eruption of the 

 first permanent tooth. The skull of a kitten ninety days old exhibits 

 all the deciduous teeth firmly in position. In the skull of a kitten 

 one hundred and thirteen days old, the permanent first and second 



