64 STRUCTURE AND ECONOMY OF THE HORSE. 



in a manner tlie larynx; whilst the shaft is intimately con- 

 nected with the root of the tongue : this part in the horse is 

 much longer than in the ox, and thus confines the motion of the 

 tongue in a great degree. The os hyoides has two long appen- 

 dages, which articulate with the temporal bone. Thus situated 

 and constituted, this bone gives great support to the soft parts 

 connected with it, whilst, at the same time, it freely admits 

 their extensive mobility. In the act of swallowing, therefore, 

 this bone is greatly called into action. 



Adjoining the pharynx arc two large spaces, called^ the 

 Eustachian "cavities, situated one on each side, and communicat- 

 ing by means of a tube with the internal ear. Their use is not 

 kn'own, but they are supposed to assist in neighing; occasionally 

 they are full of matter in strangles and other diseases of the 

 throat. — Ed.] 



CHAP. XV. 



THE VISCERA OF THE ABDOMEN, OR BELLY. 



As compared with man or with carnivorous animals, the abdomen 

 of the horse is of large size; the nature of his food requires con- 

 siderable volume in the intestines, and these, of course, demand a 

 corresponding cavity for their reception. We find it almost an 

 invariable rule, that horses with very small bellies are incapable 

 of much or long continued exertion. The abdomen is bounded, 

 anteriorly, by the diaphragm, which separates it from the chest ; 

 posteriorly, by the bones of the pelvis ; superiorly, by the ribs 

 and back bone, and their muscular coverings ; laterally, by 

 the ribs in front, and the abdominal muscles ; and, inferiorly, 

 by tlie abdominal muscles, which form their most extensive 



covenng. 



On cutting into the cavity, we perceive a smooth shining 

 membrane, called the peritoneum, which every where lines the 

 interior of the abdomen, and is also reflected on the viscera, so 

 that no two organs touch each other, this membrane being 

 interposed between them. Its use, then, is principally to pre- 

 vent friction, and to enable the almost continual motion of the 

 bowels to be executed without injury. For this purpose it 

 secretes a watery fluid, which, in the living animal, exists in 

 a vaporous form, and perfectly lubricates every part it ap- 

 proaches. 



The peritoneum is composed of dense cellular membrane, is 

 very strong, and yet extremely elastic, whereby it can accom- 

 modate itt'jlf to tlie ever-varying size and disposition of the ab- 

 dominal contents, particularly during gestation in the female. 



