Digestion. 113 



villous sac of the stomach, which forms over the surface of the 

 viscus a thick gelatinous firmly adherent coating like white 

 of egg, which cannot be washed away even by a powerful 

 jet of water. We shall later draw attention to its functions. 



The pyloric orifice of the stomach is usually large and 

 open, the cardiac is tightly closed; these two openings 

 are situated close together. There is a distinct pyloric 

 ring, behind this the duodenum is dilated, and the gut here 

 comports itself in such a singular manner (which has a very 

 important bearing on the pathology of the organ) that men- 

 tion must be made of it here. From the pylorus the 

 duodenum curves down at once and then up again, forming 

 a letter U ; so much does this remind one of a well-known 

 form of trap used in drainage, that I have described it as 

 the syphon trap of the duodenum (Fig. 8). The use of this 

 trap appears to be to regulate the passage of material from 

 the stomach into the intestines. I have shown that its 

 presence in all probability influences rupture of the stomach, 

 for the more distended the large bowels become, the greater 

 the pressure exercised on the duodenum, and in cases of 

 severe tympany the passage from the stomach to the 

 intestines is completely cut off; as fermentation still con- 

 tinues in the stomach, and the material can neither escape 

 forwards into the oesophagus, nor backwards into the bowel, 

 the coats of the viscus are completely lacerated through the 

 intense strain. 



The physiological points of interest in the structure of 

 the horse's stomach are : 1, its small size ; 2, not being in 

 contact with the abdominal wall, but resting on the colon ; 

 3, the outlet and inlet situated close together ; 4, the con- 

 tracted cardia; 5, only a portion of its surface being capable 

 of secreting a digestive fluid ; 6, the remarkable differences 

 in its mucous membrane. 



We must now return to the points which we have pre- 

 viously stated as possessing an important influence on the 

 process of gastric digestion. 



The length of time food remains in the stomach will 

 depend upon its chemical composition and bulk, also as 



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