OF DIGESTION. 159 



nearly empty, the convex border hangs downwards, and when filled, 

 it rises forwards, producing sometimes a painful feeling of disten- 

 sion. This is most felt by persons who are troubled with flatulence 

 after taking food. In such persons, if one finger be laid over the 

 stomach and struck with one of the other hand, it will sound like a 

 drum, in consequence of the quantity of air which is contained in 

 it. The oesophagus or gullet enters the great or left end of the 

 stomach, and the pyloris or small intestine commences at its smaller 

 or right end. These two orifices are upon the same level, so that 

 the food does not run out of the stomach, but can only get out of it 

 by the contraction of its coats. These are muscular, as indeed are 

 the coats of the whole intestinal canal, and are particularly strong 

 at the smaller end, where they form a ring, which contracts and 

 completely closes the communication between the stomach and 

 intestines. The stomach is lined with a velvety mucous membrane, 

 similar to and continuous with that which lines the mouth and 

 gullet. This membrane is full of minute blood-vessels, from which 

 a mucous fluid is poured, which serves at once to mingle with the 

 food and assist its digestion, and to protect the coats of the stomach 

 from injury. Accordingly, when any irritating substance is swal- 

 lowed, mucus is immediately poured out, which envelopes it, and 

 prevents, as far as possible, the evil consequences which might 

 ensue. 



GASTRIC JUICE. 



Besides the mucous, another fluid is poured into the stomach by 

 its coats, which is called the gastric juice. This is a clear ropy 

 fluid, of a saltish taste, possessing the power of dissolving all sub- 

 stances which are fit for food. It has no effect, however, on the 

 living stomach ; but we often find, on opening persons who have 

 died suddenly, with a quantity of the gastric juice in the stomach, 

 and no food, that the dead stomach itself has been dissolved, and 

 that a large irregular opening exists in its back part. 



After a meal, the stomach becomes agitated by a constant succes- 

 sion of gradual contractions, which turn the food gently back again, 

 churning it and mixing it all well together, so that it acquires the ap- 

 pearance of so much porridge or gruel, the different aliments that have 

 been swallowed becoming so blended as to form a homogeneous mass 

 of a greyish color. It is turned backward and forward for three hours 

 or more, until the delicate sense which resides in the orifice leading 

 into the intestines is satisfied that it is fit to pass further. The con- 



