THE BIGESTIVE SYSTEM. 113 



first dropped has two incisor teeth, and that two more are shortly 

 in evidence. In fourteen days time after birth two more are 

 erupted, making six then in all, and by three weeks after birth 

 "two more become visible, giving the lamb eight incisor teeth. 

 This is not by any means without exception, as frequently lambs 

 sxve dropped with all eight incisors in evidence. These are the 

 temporary or milk teeth, and as the animal progresses in age 

 they drop out, and are replaced by the permanent teeth. For 

 instance, when the lamb gets to be between one year and one 

 year and a half old the two central incisors are replaced by two 

 larger and stronger teeth, the lamb then being called a yearling. 

 By two years the tooth on either side of the centrals under- 

 goes the same transformation, and are succeeded the following 

 year or year and a half by those adjoining, so that in three and 

 a half years the sheep has six permanent teeth, and between 

 four and four and one-half years the last two temporary incisors 

 ■disappear to be replaced by permanent ones, the sheep then 

 being said to be full mouthed. While the above is substantially 

 correct and can be counted on as a general rule, yet sometimes 

 permanent teeth appear much earlier, and at others their appear- 

 ance may be protracted to a later period. After the sheep 

 possesses a full mouth the teeth rarely remain perfect for any 

 length of time, some of them becoming broken or lost. They are 

 then said to be broken mouthed. In appearance the incisor 

 teeth are chisel shaped, rather resembling the human incisors, 

 they are curved, being convex in front and concave behind, the 

 whole of the crown being covered with enamel. 



The Molar Teeth are twenty-four in number, twelve on 

 each jaw. They are firmly implanted in the jaw bones, being also 

 covered with enamel on their face. These faces are very irregular, 

 to enable them to grind tough and unyielding substances, such 

 as corn and drv ti'rass. On the sides of the base of the visililc 



