62 STRUCTURE AND ECONOMY OF THE HORSE. 



acquires carbon, it gives out caloric in a sensible form, and thereby 

 every portion of the body is supplied with heat, with th-e regu- 

 larity and precision of the most beautiful machinery. And thus 

 every animal l)ears about with him, safely packed away in the 

 cavity of the chest, a chemical apparatus, superior to any which 

 the laboratory of the chemist can supply, — an apparatus adapted 

 to all climates and all temperatures, which in one moment can 

 convert the frozen element of the northern pole into the very 

 material of physical heat. — Ed,] 



CHAP. XIV. 



THE MOUTH AND THROAT, ETC. 



[The cavity of the mouth is very spacious in the horse, which 

 is necessary in order to contain a large quantity of food, and, 

 also, to afford sockets for the large molar teeth. It is wider and 

 deeper at the upper part towards the throat than at the lower. 

 It is bounded in front principally by the anterior maxillary bone, 

 by which it is separated from the nostrils, and posteriorly by the 

 numerous muscles situated between the branches of the posterior 

 jaw bone. It is lined at every part by a mucous membrane, 

 which, however, is not immediately placed on the bone, there 

 being a thick firm substance interposed. 



These membranes are corrugated at the upper jaw, and be- 

 tween the incisor and maxillary teeth, forming what are com- 

 monly called the bars, and where horses ai-e sometimes bled : 

 these bars are also the seat of lampas. The gums of the mouth 

 are also composed of these membranes, which thus afford security 

 to the teeth. 



The sides of the mouth are formed by the cheeks, which are 

 composed of skin and membrane, sufficiently loose to admit the 

 limited motion of the jaws ; they are connected with the powerful 

 masseter muscles, which form the greater part of the bulk of the 

 face, and principally assist in the grinding motion of the jaws. 

 In the skull we find the lower jaw considerably narrower than 

 the upper ; but in the living animal this does not appear, the 

 space being occupied by the masseter muscles. 



The lips greatly assist in gathering together the food, and are 

 largely furnished witii the nerves of feeling ; they are composed 

 of skin, muscle, and membrane, and possess the powers of motion 

 and sensation in a higli degree. 



The mouth is abundantly supplied with a watery fluid called 

 saliva, particularly during mastication, when it is secreted and 

 poured in in considerable quantities. This fluid is secreted by 



