54 THE PERMANENT DENTITION. 



The incisors and premolars absorb and replace the 

 entire temporary dentition, except the shells or caps 

 described in the preceding chapter, but the canines 

 and molars are cut through the gums. 



In veterinary works, as a rule, no distinction is made 

 between a premolar and a molar, the twenty-four back 

 teeth being called either molars or grinders. Prof. 

 C. S. Tomes says the premolars and molars " are very 

 similar to one another in shape, size, and in the pat- 

 tern of their grinding surface." There is a difference, 

 however, between the respective teeth, and naturalists 

 make a distinction. The premolars (the three first 

 back teeth), which replace the temporary molars, are 

 slightly larger than the molars (the three last back 

 teeth). They have besides a backward inclination, 

 while the molars incline forward ; the respective teeth 

 are thus set toward one another. Both kinds are 

 properly called grinders. 



The permanent teeth are cut in pairs, two in either 

 jaw, the upper teeth preceding the lower from one to 

 two weeks. In the cutting of the canines, however, 

 the reverse is the rule, for the lower teeth precede the 

 upper. About a year's time elapses between the cut- 

 ting of the respective pairs of teeth ; that is, when the 

 central incisors are cut, it will be about a year before 

 the dividers will emerge. The rule is applicable to 

 the premolars and molars also, but the case is different, 

 for twenty-four of these teeth have to be cut during 



horse) ; nor do they always displace deciduous predecessors 

 (e. g., they do not all do so in the marsupials) ; so that this defi- 

 nition is not absolutely precise. Still, as a matter of practice, 

 it is usually easy to distinguish the premolars, and the division 

 into premolars and molars is useful." C. S. Tomes, "Dental 



