478 CARNIVORES. 



thicker and more obtuse as well as larger crowns than the first 

 and second milk-molars which they displace. The lower deciduous 

 sectorial is succeeded by the fourth premolar, which, as usual, 

 has a more simple crown than the deciduous tooth which it dis- 

 places. The permanent sectorial has no direct deciduous predecessor 

 and therefore must be held to be a true molar tooth, according to 

 the character assigned to those teeth in this work. The absence 

 of a tuberculate molar in the lower jaw of the immature Dog 

 brings the character of the deciduous dentition of the genus 

 Canis much closer to that of the typical members of the Car- 

 nivorous Order, and affords an interesting illustration of the law 

 that ' unity of organisation is manifested directly as the proximity 

 of the animal to the commencement of its development. '(1) The 

 succession of two tubercular molar teeth behind the permanent 

 sectorial tooth in the adult or permanent dentition of the lower jaw 

 carries the genus Canis farther from the type of its Order, and 

 stamps it with its own proper omnivorous character : and this con- 

 tributes to adapt the Dog for a greater variety of climate, food, 

 and other circumstances, all tending in an important degree to fit 

 that animal for the performance of its valuable services to man. 



In no other genus of Quadruped are the jaws so well or so 

 variously armed with dental organs : notwithstanding the extent 

 of the series, the vacancies are only sufficient to allow the in- 

 terlocking of the strong canines. These are efficient and for- 

 midable weapons for seizing, slaying, and lacerating a living 

 prey : the incisors are well adapted by their shape and advanced 

 position for biting and gnawing : the premolars, and especially 

 the sectorials, are made for cutting and coarsely dividing the 

 fibres of animal tissues, and the tuberculate molars are as admirably 

 adapted for cracking, crushing, and completing the comminution 

 of the food, whether animal or vegetable. 



Amongst the aberrant species of Canida it is interesting to 

 find in the Proteles, which presents the most anomalously simple den- 

 tition in the adult state, a much greater conformity with the common 



(1) This Law is defined and exemplified in my ' Lectures on the Invertebrate Animals,' 

 p. 368, 8vo. 1843. 





