DISEASES OF DOMESTIC ANIMALS. 143 



Then this follicle or bag becomes separated into a sheet-sac ; this is 

 called the sacular stage. Then a cavity appears between the teeth, 

 called the cavity of reserve. The permanent teeth soon become 

 developed ; press upon and cause absorption of the temporary, until 

 in some cases nothing but the crown is left, which drops out. There 

 is some difference in the number of teeth in the domestic animals. 



Incisors. Canine. Molars. Bicuspid. 



Man J % I % ^32 



Horse ^ f -}| -S =40 



Ox % % \i - =32 



Dog I I \i I =42 



Pig I S if I -44 



The central incisors appear at birth, or in two or three weeks ; the 

 lateral in about nine weeks ; the comer in about nine months, and 

 they are up and in wear at one year old. The first, second and third 

 molars appear as temporary teeth at or soon after birth. The first 

 temporary molar is replaced by a permanent one when the horse is 

 from two to three years old. The second and fourth appear, perhaps, 

 about the same time when he is about four years old. The two per- 

 manent central incisors appear from two and a half to three years — 

 at three they are up and in wear. The lateral from three and a half 

 to four, and are up and in wear at four. The corner from four and a 

 half to five, and up and in wear at five. But they do not come just 

 the same in all animals. I have seen a full mouth of permanent 

 incisors at four years old. Sometimes the posterior table surface does 

 not wear down with the anterior — due to the way in which the teeth 

 grow. This is called shell mouth, and you might mistake an eight- 

 year-old for a six-year-old. Young teeth are widest from side to side; 

 in old ones they are widest from before back. You can tell the age 

 pretty well up to six or seven years. It is well to look at the upper 

 jaw. Sometimes the upper jaw overlaps the under, giving rise to 

 what is called a parrot mouth. At six years the posterior table sur- 

 face of the corner incisors is up and in wear, and the mark is begin- 

 ning to wear out of the central teeth, and when you see the mark 

 worn out of the central incisors, you may say he is six years old. At 

 seven the mark is worn out of the lateral, and at eight out of the 

 corner incisors. By the upper teeth, which do not wear so fast as the 

 others, we can determine the age pretty correctly up to twelve years. 

 At nine the mark is worn out of the lateral, and at about eleven or 

 twelve out of the corner incisors. And even after this, by watching 

 the manner in which they grow, you can tell something of the age. 

 You are also assisted by the tushes, which at first are small, but grow 

 as the animal grows, or in some cases they wear down, and an accumu- 

 lation of cement surrounds them, which tells you the animal is pretty 

 old. Running horses, that are entered as such, date their birth from 

 the first of January — although born in September, he would be called 

 one year old on the first of January. Until lately, in some of the 

 Southern of the United States, it was counted from May. Foals are 

 generally dropped in the spring. Sometimes you have to give an 

 opinion as to the age of the ox, which has no incisors in the lower 

 jaw, but the place is occupied by a cartilaginous pad, and there are 

 eight incisors in the lower jaw, which are called shovel-shaped, and 

 are not so firmly set in the alveoli as in the horse. It is a natural 

 condition, as a general thing, and not the result of disease. The 

 same three tissues enter into their formation. The two incisors in 



