390 



THE TEETH OF THE HORSE 



operation. As these rudimentary organs have a very slight hold in the 

 jaw, a very moderate amount of force will dislodge them, and the horse 

 is neither better nor worse for the performance. 



Reference to the section on the conformation of the horse will convince 

 the reader that the small conical tooth, to which so much importance is 

 attached, is really the vestigial remains of the first pre-molar, which is 

 a well-developed tooth in the top and bottom of both sides of the mouth 

 in many of the ancient ungulate mammals, making a row of seven instead 

 of six molars, of which four were pre-molars and three true molars. The 



gradual diminution in size of the first 

 pre-molar may be traced in the fossil 

 remains of horse-like animals of the ter- 

 tiary formation. In the horse of the 

 present time the first pre-molar has 

 altogether ceased to exist in the bottom 

 jaw, and only remains in the top jaw 

 as a rudimentary and occasional struc- 

 ture, which is frequently shed when the 

 temporary pre-molars are exchanged for 

 permanent. A peculiarity in the horse's 

 mouth more difficult to account for than 

 that above referred to is the space which 

 exists between the molar teeth and the 

 incisors. This space did not exist in the 

 most ancient mammals, but in the Phena- 

 codus there were some indications of it, 

 and it becomes more distinct through the 



series of horse-like animals which will be described in the chapter on the 

 peculiar features of the conformation of the horse. In the male of the 

 horse family the space is partly occupied by the canine teeth or tusks; in 

 the mare these organs are either entirely absent or are merely rudimentary. 

 Form and Arrangement. Some knowledge of the form and general 

 arrangement of the different orders of teeth are essential for an intelligent 

 appreciation of the changes which take place owing to wear in one direction, 

 and the growth of the organs in the other. 



The incisor teeth are chiefly used as a means of judging the age after 

 permanent dentition is complete. Up to that time the change from 

 temporary to permanent organs, both incisors and molars, affords important 

 indications of the age of the animal from birth up to the age of five years. 



For the purpose of distinguishing the temporary from the permanent 

 organs, an illustration will be more useful than a written description, and 



Fig. 600. Permanent and Temporary 

 Incisors of Horse 



