THE INCISORS ADAPTED FOR GRAZING. 57 



grow till about the seventh year, being, to use Prof. 

 Owen's words, "implanted in the socket by an undi- 

 vided base." 



The incisor teeth, which will average about two 

 inches and a quarter in length, are characterized by 

 distinct curvatures, the outer sur- 

 face, according to Surgeon John 

 Hughes, forming a third of a cir- 

 cle, the inner a fifth. Were a string 

 drawn from the crown of one of 

 these teeth to the apex of the 

 root, the figure would resemble a 

 bow. The upper teeth are larger 

 than the lower, and there is a dif- 

 ference in size of the respective 

 teeth in both jaws, the centrals 

 being larger than the dividers, 

 and the dividers larger than the 

 corners. 



The incisors meet edge to edge, 

 being thus admirably adapted for 

 the purposes of grazing, and at 



A virgin incisor tooth : pos- 



the age of six years the bodies are M*tfa.-aowm 

 nearly perpendicular one to the other. They form 

 nearly semicircular figures, and, when the mouth is 

 closed, present a rounded outer surface. 



" The incisors," says Prof. Owen, "if found detached, 

 recent or fossil, are distinguishable from those of the 

 ruminants by their greater curvature, and from those 

 of all other animals by the fold of enamel which pen- 

 etrates the body of the crown, from its broad, flat sum- 

 mit, like the inverted finger of a glove." 



The fold of enamel, which is commonly called the 

 ''mark," but which is also known as the infundibuluni. 



