THE TEETH 



425 



ERUPTION OF PERMANENT UPPER 

 CANINE AND THIRD UPPER PRE- 

 MOLAR TEETH ; PERMANENT UP- 

 PER MOLAR, DECIDUOUS CANINE 

 AND SECOND AND THIRD MOLARS 

 IN POSITION. 



sectorial descends above the third deciduous molar, between its ex- 

 ternal and internal fangs, and thus forces it directly downward ; the 

 anterior cusp of the permanent sectorial appears just internal to the 

 posterior part of the cutting blade of the 

 deciduous sectorial ; and the internal cusp FIG. 349. 



behind and medial to its internal 'fang. 



The permanent upper canine and sec- 

 torial are in place before the milk sectorial 

 is lost and before the second upper premolar 

 is fully grown (Fig. 350). 



While the permanent upper canine is 

 descending, the lower permanent canine 



pushes out the deciduous tooth. By this time the permanent lower 

 molar is entirely above the gum and the first lower premolar is coming 



through the bony alveolar border on the inner 

 side of the corresponding deciduous molar (Fig. 

 351) ; as it pushes out this tooth, the second 

 lower premolar, the last tooth, appears on the 

 inner side of the deciduous sectorial. By this 

 order in the succession of the permanent teeth 

 a cat has two sets of sectorial teeth in position 



at one and the same time ; thus is precluded all danger of loss, even 

 temporarily, of this most important element in the dentition. 



FIG. 350. 



ERUPTION OF SECOND UP- 

 PER PREMOLAR TOOTH ; 

 SECOND DECIDUOUS MO- 

 LAR STILL IN POSITION. 



FIG. 351. 



FIG. 352. 



ERUPTION OF PERMANENT LOWER MOLAR 

 AND FIRST LOWER PREMOLAR TEETH ; 

 DECIDUOUS LOWER MOLARS ALONE RE- 

 MAINING. 



ERUPTION OF FIRST AND SECOND LOWER 

 PREMOLAR TEETH; DECIDUOUS SECOND 

 MOLAR STILL PRESENT. 



DETERMINATION OF THE PERMANENT TEETH. 



The upper incisors have a transverse groove across their posterior 

 surfaces. The first and second have three almost equal cusps on their 

 cutting edge, and are so symmetrical that they present no characters 

 whereby the right teeth may be distinguished from the left. 



The third incisor has a conical crown and an oblique posterior 



