THE BRAIN. 107 



The calculation of the age of the hog by means of reference to 

 the mouth, has not yet been carried beyond three years ; no writer 

 seems to have gone much beyond the protrusion of the adult middle 

 teeth of the lower jaw. 



The hog is born with two molars on each side of the jaw ; by the 

 time he is three or four months old, he is provided with his incisive 

 milk teeth and the tushes ; the supernumerary molars protrude be- 

 tween the fifth and seventh month, as does the first back molar ; the 

 second back molar is cut at the age of about ten months, and the 

 third generally not until the animal is three years old. The upper 

 corner teeth are shed at about six or eight months, and the lower 

 ones at about seven, nine, or ten months old, and replaced by the 

 permanent ones. The milk tushes are also shed and replaced be- 

 tween six and ten months old. The age of twenty months, and from 

 that to two years, is denoted by the shedding and replacement of 

 the middle incisors, or pincers, in both jaws, and the formation of a 

 black circle at the base of each of the tushes. At about two years 

 and a half or three years of age, the adult middle teeth in both 

 jaws protrude, and the pincers are becoming black and rounded at 

 the ends. 



After three years, the age may be computed by the growth of the 

 tushes ; at about four years, or rather before, the upper tushes begin 

 to raise the lip ; at five they protrude through the lips ; at six years 

 of age, the tushes of the lower jaw begin to show themselves out 

 of the mouthTahd assume a spiral form. These acquire a prodigi- 

 ous length in old animals, and particularly in uncastrated boars ; 

 and as they increase in size they become curved backwards and out- 

 wards, and at length are so crooked as to interfere with the motion 

 of the jaws to such a degree that it is necessary to cut off these 

 projecting teeth, which is done with the file or with nippers. ( Traite 

 de VAge du Ckeval, du B&vf, du Mouton, du Chien, et du Uochnn t 

 par N. F. et J. Girard.) 



THE BRAIN. 



This important organ is not SQ large as from an external view of 

 the cranium we should be led to suppose, the frontal and sphenoidal 

 sinuses contracting the limits of the cranial cavity and rendering it 

 narrow ; it is, however, considerably larger in proportion to the size 

 of the animal than that of the ox or sheep, being about l-500th part 

 of the weight of the animal, while that of the ox is only l-800th part, 

 and that of the sheep only l-750th part. The irregularities of the 

 surface, or those prominences and depressions which define the organs 

 in phrenology, are more marked in the pig than in the horse, taking 

 the size of the animal into consideration, but not so much marked 

 AS in the dog. 



