THE TEETH 



405 



in a typical mammalian dentition, which is regarded as containing 



forty-four teeth : i ^, c -, pm -, m ^. Inasmuch as the cat has but 



31 4 o 



three upper premolars, the missing one cannot have been between the 

 premolars and the molars. Its first upper premolar, therefore, corre- 

 sponds with the second upper premolar of the typical dentition, the 

 second with the third, and the third with the fourth. In the lower jaw 

 the first premolar corresponds with the third typical premolar, and the 

 second with the fourth. The premolar teeth are sometimes numbered 

 from behind forward ; thus what we call the third upper premolar 

 is known as the first, the second as the second, the first as the third. 

 In the following descriptions I have thought it best to number the 

 teeth in their natural order, without regard to theoretical relationship. 



The premolars and molar teeth taken together constitute the cheek- 

 teeth. 



If we examine the second lower premolar (Fig. 320) we observe 



FIG. 320. 



Crown, 

 Anterior Basal Cusp 



Cingulum. 



Principal Cusp. 



Posterior Basal Cusp 

 Heel or Talon. 



-Neck. 



Anterior Fang v , J| ^,/j Posterior Fang. \ Jjj I If Anterior Fang. 



\j$r \WJi 



INNER ASPECT. OUTER ASPECT. 



Anterior Basal 

 Cingulum. 



Outer Side. 



Talon. 



Principal Cusp. 

 Posterior Basal C,sp, 



Cingulum, 

 Neck 



Posterior Fang. \) I i||| Anterior Fang. 



POSTERIOR ASPECT. 

 RIGHT SECOND LOWER PREMOLAR TOOTH. 



that it is divided into two principal parts, (1) the crown, which pro- 

 jects above the gum and is covered with hard, glistening enamel, and 

 (2) the roots, or fangs, which are contained in the alveoli of the jaw 

 and are covered with a rough substance resembling bone, known as 



