Teeth. 117 



sets of teeth, the first set being termed the milk dentition^ and 

 the last the permanent dentition. The permanent incisors and 

 the first few molars, on this account termed premolars, have 

 predecessors in the milk dentition. The arrangement of the 

 teeth in mammalian jaws is commonly expressed by dental 

 formulae, which serve to show at a glance the number of the 

 teeth and their nature. Only one side of each jaw is taken 

 in representing the teeth, so that the number as given in the 

 formulae must be doubled in order to give the full number. 

 The milk dentition of the rabbit is represented by the following 

 formula : di. \, dc. ^, dm. \ ; the permanent thus : i. y,, c. -j-, 

 pm. f, m. f. i., c, pm., m., respectively stand for incisors, 

 canines, premolars, molars ; a d before each of these letters 

 means deciduous, or milk incisor, etc. 



' Diphyodont is the technical term for a mammal with two sets of teeth. 



