594 REVIEW-GIRARD ON THE TEETH, &C, 
have their surfaces flattened, yet studded with irregular points. 
The six superior molars, larger than the inferior ones, have the 
same general conformation with them. Their surface resembles 
that of the three inferior back molars. From this description of 
them it will appear that the grinders of the hog tear and crush 
and break down the substances exposed to their action. 
The little pig, when born, has four molars in each jaw, two on 
the right and two on the left; and he is provided with all his 
temporary teeth when he is three months old. According to M. 
Viborg, the protrusion of the supernumerary molars occurs at from 
five to six and a half months, and the first back molar is cut about 
the same time. The second back molar makes its appearance 
at ten months; but the last does not ordinarily find its way 
through the gum until the animal is three years old. The re¬ 
placement of the second temporary molar happens from fifteen 
to eighteen months. The first temporary front molar continues 
longer, and is shed at two years old. 
Section III.— liecapitulation. 
The calculation of the age of the pig, as evidenced by the teeth, 
has not yet been pushed beyond three years; it has stopped at 
the protrusion of the adult middle teeth of the lower jaw. 
It has been seen that, at three or four months, the young pig 
is provided with all his incisive milk teeth, as well as the tushes; 
and the successive replacement of these teeth is the only sure 
guide to the knowledge of his age. ' 
From six to ten months. —The shedding and replacement of the 
corner teeth—the change of the upper comer teeth preceding 
that of the low^er ones by two or three months; the milk tushes 
give place to the permanent ones. 
From twenty months to two years. —The change of the pincers 
in both jaws, and the formation of a black circle at the base of 
the tushes. 
From two and a half to three years. —The protrusion of the 
adult middle teeth in both jaws ; the pincers are black, shagrined, 
and a little rounded at the extremity. After three years, the age 
is appreciated by the growth of the tushes, which continue to in¬ 
crease in length and thickness as long as the animal lives. Be¬ 
tween three and four years, the upper tushes begin to raise the 
lip, and at five years old they protrude through the lips. At six 
years of age the tushes of the lower jaw shew themselves out of 
the mouth, and begin to turn in a somewhat spiral form. At 
this period, also, the eyebrows become wrinkled, and the lateral 
eminences of the forehead, caused by the roots of the tushes of 
the upper jaw, become more projecting. After seven years, the 
