PECULIAE TO nOKSES. 109 



composed of two membranes, united together by cellular tissue ; the 

 external one is of a fibrous character, dense and strong; the inter- 

 nal is smooth and glistening, and very much resembles that found 

 within the cavity of the chest, known as the pleura ; its function is 

 to secrete a fluid called the liquor pericardii ; this fluid being inter- 

 posed between the internal surface of the pericardium and the mem- 

 brane proper of the heart, guards against friction. It is within the 

 pericardium that we occasionally meet with a disease known as 

 hydrops pericardii. 



REASONS WHY HORSES DO NOT BREATPIE THROUGH 

 THEIR MOUTHS ! 



The soft palate, as it is technically called, velum palati, is a sort 

 of curtain affixed to the roof of the mouth, in the region of the pal- 

 atine arch ; it has a free edge which rests upon the epiglottis.* It 

 slants in a posterior direction, so that anything in the shape of food 

 coming from the mouth, raises and pushes it backward ; but any- 

 thing coming from the oesophagus or trachea, pushes it forwai'd and 

 downward, closes it, and thus prevents all egress. So that air is 

 expired and respired through the nasal outlet, and all matter vom- 

 ited from the stomach must also be ejected through the nostrils. In 

 the act of coughing, however, which is a spasmodic action, the air 

 returns in body and with force sufficient to raise the velum palati, so 

 that a passage through the mouth is, at the moment, secured. 



The mechanism of the soft palate is as follows : Its composition 

 is nearly the same as that of the hard palate, yet it abounds moi-e in 

 glandular substance and muscular fibre ; by means of the levator 

 palati, its substance is raised. On the lateral and internal portion of 

 the membrane we find bundles of muscular fibres, constituting a pair 

 of muscles known as depressors^ which aid in retaining the palate 

 in its place, viz., on the epiglottis. From the above brief remarks 

 the reader will perceive that it is not natural for ahorse to breathe 

 through his mouth. 



, USE OF THE HARD PALATE, OR 'BARS" OF A 

 HORSE'S MOUTH. 



, The palate of the horse's mouth is divided, according to custom, 

 into two parts, denominated soft and hard. The soft portion runs 

 in a superior and posterior direction, to the region of the base of the 

 tongue, and serves to separate the mouth from the fauces. f The 

 hard palate is marked crosswise by prominent ridges and furrows 

 from side to side, which are called the " bars." They serve to aid 

 in keeping the food within the mouth during mastication. Were it 

 not for this contrivance {the horse's head being pendulous), it would 



* Cartilage at the root of the tongue. 



+ Fauces. The back part of the mouth. The soft palate is a mere expanded uvula. It origi- 

 nates at the arch of the palate bone, where the hard palate terminates. 



