CHAPTEE n. 



MASTICATION, DIGESTION AND ASSTMILATION. > 



23. Prehension. — The horse when grazing gathers herbage 

 with the lips, which are very sensitive, and act with great mo- 

 bility. The food thus gathered is severed with the incisor or 

 front teeth of the upper and lower jaws. When feeding on hay 

 and grain, the horse still makes free use of the lips in working 

 the food into the mouth. 



The ox seizes herbage with the outstretched tongue, and by a 

 swinging motion of the head severs it as it passes between the 

 teeth in the lower jaw and the cartilaginous pad of the upper jaw. 



The sheep, like the ox, has no teeth in the upper jaw; like the 

 horse, it makes free use of the lips when grazing. The horse in 

 grazing crops the herbage nearer to the ground than does the ox, 

 and the sheep still closer than the horse. 



The shape and direction of the front teeth of the hog show an 

 onmiverous feeder. Probably the grazing quality of the hog 

 varies considerably with the breed, and also in different strains 

 of the same breed, the skulls and jaws of hogs presenting re- 

 markable variations in size and shape. 



24. Mastication. — The food consumed by the animal is reduced 

 to fineness by the molar teeth, assisted by the lips, tongue and 

 cheeks, which pass it to the place for grinding and hold it in 

 position. With herbivorous animals the lower jaw is much 

 narrower than the upper. In the horse, when the upper and 

 lower grinders of one side are in contact, those of the lower jaw 

 on the other side are nearly or quite an inch to the inside of their 

 mates above, so that grinding is possible on but one side of the 

 mouth at a time. As mastication proceeds, the feed is mixed 



1 Most of the text and tables in this chapter are adapted from the 

 Physiology of the Domestic Animals, by Eobert Meade Smith, which 

 excellent work should be consulted by the student seeking further infor- 

 mation on these subjects. 



