40 



AGE OF THE DOMESTIC ANIMALS. 



Inferior Molars. — The anterior and posterior faces are 

 flat, except tlie posterior of the sixth tooth and the anterior of 

 the first tooth, which are replaced by sharp edges. The ex- 

 ternal faces have one longitudinal gutter hi the first five teeth 

 and two in the sixth tooth. The internal faces have three 

 gutters in the first and sixth teetli and a variable number in the 

 others. The free extremity is triangular in the first and sixth 

 molars and quadrilateral in the others ; but these are narrower 

 from side to side than from in front to behind. They are longer 

 on their internal border than on the external, and have the Old 

 Englisli ^ turned with the loops outward. The imbedded por- 

 tion is bicuspid in the first five teeth and unicuspid in the 

 sixth. The divisions of the roots diverge; each contains a 

 cavity for the pulp. 



DEVELOPMENT AND STRUCTURE OF THE MOLARS. 



[n the superior molars the papilla of the enamel in the 

 B A 



Fig; 28. 



A riglit superior molar taken from the dental follicle A, view from free 

 end; B, view from tlie imbedded portion; a, anterior infundibula; a', posterior 

 infundibula; e, external border of the infnndibula ; i, internal border of the in- 

 fundibula; c, accessory column of the anterior infnndibula. 



germinal sack is double and penetrates into the tooth, forming, 

 practically, two infundibula, one anterior and one posterior, in- 

 stead of one cup, as in the incisor teeth. The papilla of the 

 pulp makes five diverticula, which almost appear to be as many 

 separate cavities. 



In the inferior molars tliere are two infundibula, one occu- 

 pying the middle portion of the tooth and one toward the an- 

 terior portion, which allows us to recognize a left-hand inferior 



molar from its right-hand homologue. 



The arrangement of the 



