494 



DIGESTIVE SYSTEM OF THE DOG 



from the corner incisor by an interval into which the lower canine is received when 

 the jaws are closed.^ The lower canine is close to the corner incisor. The root is 

 about an inch (ca. 2 to 3 cm.) long and is flattened laterally. 



The cheek teeth are typically -f-, but in brachycephalic breeds they are com- 

 monly reduced to f , and in extreme cases even to f. The reduction occurs at either 

 end or at both ends of the series.* The first tooth appears only once. The fourth 

 tooth of the upper row and the fifth of the lower row are much larger than the rest, 

 and are termed sectorial or camassial teeth. From these the teeth diminish in size 

 both forward and backward. The upper and lower teeth do not correspond, but 

 rather dovetail. The teeth behind the sectorial ones are tuberculate, i. e., have 



Fig. 435.— Skull of Adult St. Bernard Dog, Sculptured to Show the Embedded Parts of the Teeth. 

 11-3, Incisors; C, canines; Pl-4, premolars; Ml-3, molars. 



rounded eminences on the masticatory surface. The others are all sectorial in 

 character, i. e., have sharp-edged, pointed projections, the middle one being the 

 most prominent. The premolars are laterally compressed, and are separated by 

 intervals from the canines and from each other, except in the brachycephalic 

 breeds. The upper molars have wide, somewhat quadrangular crowns, and three 

 roots. The crown of the upper fourth premolar (Dens sectorius) is divided into 

 two pointed lobes and has an antero-medial tubercle; it has three roots. The 



^ In the bull-dog, which is very prognathic ("undershot"), the lower canines are opposite 

 to or slightly in front of the plane of the upper incisors, and the upper canines are about opposite 

 to the first lower cheek teeth. In the epignathic ("overshot") dachshund the lower canines are 

 under or slightly behind the upper ones. 



^ Increase in number also occurs, the supernumerary teeth being at either end of the series. 

 The occurrence of a third upper molar is not rare. 



