THE HEAD AND NECK. 139 



horse, pointing to a different condition in the ances- 

 tral state. 



The diminutive first premolars should probably 

 be regarded as teeth of the permanent set, and, con- 

 sidering how near they are to disappearance, they 

 could hardly be expected to have milk predecessors, 

 especially as such are frequently absent in other ani- 

 mals in which these teeth are fairly well developed. 



The functional milk molars are three in number, 

 corresponding in succession with the three functional 

 premolars of the permanent set. The middle one 

 resembles the intermediate permanent molars, but 

 the first and third have their extremities somewhat 

 narrowed, so that the grinding-surface of the whole 

 block presents a representation on a smaller scale of 

 that of the permanent set. The crowns are compara- 

 tively short, and distinct roots are formed by the 

 time the growth of the tooth is complete. As the 

 permanent teeth rise up below them these roots are 

 absorbed, and nothing remains but the worn base 

 of the crown, which is finally cast off as its successor 

 becomes fitted to take its place. 



Time of Appearance and Order of Succession of the 

 Teeth. The eruption or cutting through the gums 

 of the temporary teeth commences at about the 

 time of birth, and is complete before the end of the 

 first year, when the young animal has its full set of 



