The Digestive System. 



35 



erals appear; at six to nine months the corners show. 

 The permanent incisors appear at three, four and five 

 respectively, the tusks (canines) from the fourth to the 

 fifth year; thus a horse is said to have a full mouth (a 

 complete set) at five years. Soon after that time changes 

 can be seen to have taken place in the incisors as follows: 

 at six years the black mark disappears from the central 

 "incisors of the lower row, at seven from the lower later- 

 als, at eight from the corner teeth of the lower row. 

 Beyond that age the signs are not as reliable, yet gener- 

 ally the black marks disappear from the upper centrals 

 at nine, the laterals at ten, and from the upper corners 

 at eleven. A general idea of the age after eight years 

 may be obtained by noting the shape of the teeth, owing 

 to the fact that as the animal grows older the incisor 

 teeth become narrower from side to side and deeper from 

 front to back, assuming gradually and consecutively 

 square, triangular and round appearances. The follow- 

 ing diagram represents the time at which the incisors 

 appear and will be a help in determining the ages of 

 the horse, ox and sheep: 



HORSE. 



\ 1 — 3 years. 



2—4 years. 

 3 — 5 years. 



OX AND SHEEP. 



Ox: 1—1$ years 

 2 — 2i years 

 3 — 2f years 

 4 — 3 years 



Sheep: 1—1 year 

 2 — 2 years 

 3 — 3 years 

 4 — 4 years 



