346 THE PRACTICE OF VETERINARY MEDICINE. 



l^ermanent and four temporary. About the age of three 

 years and six months the lateral incisors appear, and are 

 up and in wear when the colt reaches the age of four years. 

 At about this time the fifth permanent molar, being the 

 third in the jaw, makes its appearance, and is cjuickly 

 followed by the sixth permanent molar, which is also the 

 sixth in the jaw ; and at the age of four years the colt has 

 all of his permanent molars, numbering twenty- four, up and 

 in wear, and no temporary molars. Between four and five 

 years of age is when the permanent corner incisors appear, 

 and at five years of age they are up and in wear. At this 

 period also the canine teeth appear in the male, and the 

 mouth is complete, no further changes taking place. Hence 

 at five years of age the horse is pronounced to have a 

 full mouth. Occasionally a horse will be met with having 

 a full mouth at the age of four years, but such cases are 

 extremely rare. Sometimes the posterior borders of the 

 corner incisors do not come up as they should. Such a 

 condition constitutes what is known as a shell mouth. 

 Such a mouth may very easil}^ cause an eight-year-old 

 horse to be mistaken for a six-year-old. The tusks, or 

 canine teeth, make their appearance only as permanent 

 teeth. In some cases they do not appear in the upper jaw 

 until the animal is between five and six years old. When 

 the incisor teeth of the upper jaw overlap, or project 

 further forward than those of the lower jaw in such a 

 manner that they do not meet, it constitutes a condition 

 known as parrot mouth, so called from the resemblance to 

 the beak of a parrot. At the age of six years the infundi- 

 bulse are worn entirely out of the central incisors, two- 

 thirds worn out of the lateral and one-third worn out of 

 the corner incisors. At seven years old the table surfaces 

 of the central and lateral incisors are found to be perfectly 

 smooth, while the infundibul^e of the corner incisors may 



