168 PHYSIOLOGY AT THE FARM. 



ORGANS OF NUTRITION IN THE DOG. 



Teeth. The teeth in the dog consist of incisors, canine 

 teeth, and molar teeth. A full-grown dog has usually forty- 

 two teeth in all namely, twenty in the upper jaw, and 

 twenty-two in the lower jaw. Besides these there are some- 

 times supernumerary teeth. The incisor teeth are six in 

 each jaw; the canine or tusks are four in all namely, one 

 on each side of each jaw ; and the molar on each side 

 are six in the upper jaw and seven in the lower jaw. The 

 incisor teeth are not all of the same size. In the lower jaw the 

 two central incisors or pincers are the largest and strongest ; the 

 incisor on each side of these is somewhat less, and the corner 

 incisor on each side is small and weak. In the upper jaw, 

 however, the corner tooth on each side is larger than the ad- 

 jacent incisor between it and the corresponding pincers ; these 

 corner teeth of the upper jaw are somewhat apart from the 

 neighbouring teeth, and terminate in a conical point, curved 

 a little inwards and backwards. The surface of the incisors has 

 an interior cutting edge, and within they exhibit a depression. 

 The terminating edge is divided into three lobes, the middle of 

 which is the largest; but this lobed appearance is at length 

 effaced by the wearing down of the edge. The incisor teeth, 

 when newly cut, are flat on the sides, and bent somewhat back- 

 wards, forming a cavity in which a pulpy substance is enclosed. 



The cuspidate teeth take their name, " canine," from their 

 conspicuous appearance in the dog. These teeth are conical, 

 and inserted in the jaw close to the suture between the upper 

 jaw and the intermaxillary bone. They are of great strength, 

 the fang thicker and longer than the enamelled crown. The 

 crown is conical, slightly recurved, sharp-pointed, convex in 



