The Inner (Alimentary) Tube and Its Respiratory Derivatb 



Fig. 42. (A) Tricoiiodont tooth of Dromatherium. (B) Tritubercular tooth of 

 Spalacotherium. (C) Interlocking of upper (dark) and lower (light) tritubercular 

 molar teeth (after Osborn). (D) Molar of Erinaceus. (E) Molar of horse (selenodont 

 type), (c) Cingulum; (m) metacone (metaconid); (pa) paracone (paraconid); 

 (pr) protocone (protoconid) ; (t) talon. (Courtesy, Kingsley: "Comparative 

 Anatomy of Vertebrates," Philadelphia, The Blakiston Company.) 



i CANINE 



INCISORS 



PREMOLARS / M _ 0L f lR ^. 



^PREMOLARS 



^CANINE 



Fig. 43. Human teeth viewed from the left side. The human dental formula is: 

 i 2 2, c'i, pm 2 2. m 3 3. As a result of the shortening of the human jaws the third molars 

 frequently do not erupt. The elongated root of the canine tooth suggests that, as 

 in lower primates, the ancestors of man may have had fangs. (After Braus. 

 Courtesy, Neal and Rand: "Chordate Anatomy," Philadelphia, The Blakiston 

 Company.) 



