THE HEAD AND NECK. 141 



from the wear of the incisor teeth,* though this de- 

 pends to a certain extent upon the hardness of the 

 food and other accidental circumstances. 



THE LIPS. 



The lips of the horse are remarkably sensitive and 

 flexible. They can be stretched out in various direc- 

 tions, and are much used in gathering food into the 

 mouth. Any one who has seen a horse take a small 

 piece of sugar from a child's hand will appreciate the 

 delicacy and efficiency of these organs as instruments 

 of prehension. They present a great contrast to the 

 thick rigid lips of the ox, in which animal the tongue 

 plays a more important part in the duty of obtaining 

 food. Flexible and prehensile lips are characteristic 

 of the Perissodactyles. In most species of rhinoceros 

 the upper lip is prolonged to a point in the middle 

 line, which acts almost like a finger, and in the tapirs 

 it joins with the nose to form a flexible and very mo- 

 bile snout or short proboscis. 



THE NOSTRILS. 



The nostrils of the horse are large and very dilat- 

 able, allowing of the admission of a greater or less 



* These are very fully described and illustrated in a 

 pamphlet called Dentition as indicative of the Age of the Ani- 

 mals of the Farm, by Professor G. T. Brown, 2d edit. 1889. 



