THE STOMACn. 275 



the cardia it is continuous Numerous small openings are 

 visible upon its inner surface, through which issues a mucous 

 fluid, the product of follicular glands underneath, which is 

 useful in the process of digestion, and where it may be said 

 properly to commence. This is called the gastric juice, which 

 mixes with the food already softened, and converts it into that 

 fluid substance called chyme. 



r. The margin which separates the cuticular from the villous 

 portions. 



d. The entrance from the gullet into the stomach. The circular 

 lavers of muscles which invest this part are very strong and 

 thick. By their powerful contractions they assist in rendering 

 it difficult for the food to be returned or even vomited. This 

 orifice is called the cardiac orifice, in consequence of its con- 

 tiguity to the heart. It is constantly closed by strong muscular 

 fibres, except when the food is passing through it into the 

 stomach. Although this assists materially in preventing the 

 return of the food, it is the construction of the soft palate 

 which mainly contributes to the prevention of vomiting in ihe 

 horse. 



f. The oesophagus, or gullet, through which the food is conducted 

 from the pharynx into the stomach. It has its commencement 

 in the pharynx, and is there placed at the upper and back part 

 of the lai'ynx, the first part of its course being behind the 

 trachea, betw^een it and the cervical vertebrit. After proceed- 

 ino- a short way down, it inclines to the left, and soon after 

 makes its appearance altogether on the left side of the trachea. 

 and continues so in its passage down the neck. This will 

 explain what has puzzled many, why we look for the bolus 

 durinw the act of swallowing on the left, and not on the right 

 side of the animal. Accompanying the trachea, tlie oesophagus 

 enters the chest between the first two ribs, at which part, 

 runnino- above that tube, it diverges from the trachea, and in 

 connexion with the superior mediastinum, and traversing that 

 cavity a little way below and to the right of the aorta. 



«. The communication between the stomach and the first intestine. 



«. A small orifice through which a portion of the secretion of the 



pancreas enters the intestines. Its direction will be seen by 



the probe which is passed through it. The pancreas, oi,hei> 



