FOOD AND DIGESTION. 365 



digested even inclosed in perforated tubes, and consequently protected 

 from mechanical influence. 



The normal actions of the muscular fibres of the human stomach 

 appear to have a three-fold purpose: (1) to adapt the stomach to the 

 quantity of food in it, so that its walls may be in contact with the food 

 on all sides, and, at the same time, may exercise a certain amount of 

 compression upon it ; (2) to keep the orifices of the stomach closed until 

 the food is digested; and (3) to perform certain peristaltic movements, 

 whereby the food, as it becomes chymified, is gradually propelled toward, 

 and ultimately through, the pylorus. In accomplishing this latter end, 

 the movements without doubt materially contribute toward effecting a 

 thorough intermingling of the food and the gastric fluid. 



When digestion is not going on, the stomach is uniformly contracted, 

 its orifices not more firmly than the rest of its walls; but, if examined 

 shortly after the introduction of food, it is found closely encircling its 

 contents, and its orifices are firmly closed like sphincters. The cardiac 

 orifice, every time food is swallowed, opens to admit its passage to the 

 stomach, and immediately again closes. The pyloric. orifice, during the 

 first part of gastric digestion, is usually so completely closed, that even 

 when the stomach is separated from the intestines, none of its contents 

 escape. But toward the termination of the digestive process, the pylorus 

 seems to offer less resistance to the passage of substances from the stom- 

 ach; first it yields to allow the successively digested portions go through 

 it; and then it allows the transit of even undigested substances. It ap- 

 pears that food, so soon as it enters the stomach, is subjected to a kind 

 of peristaltic action of the muscular coat, whereby the digested portions 

 are gradually moved toward the pylorus. The movements were observed 

 to increase in rapidity as the process of chymification advanced, and were 

 continued until it was completed. 



The contraction of the fibres situated toward the pyloric end of the 

 stomach seems to be more energetic and more decidedly peristaltic than 

 those of the cardiac portion. Thus, it was found in the case of St. Mar- 

 tin, that when the bulb of the thermometer was placed about three inches 

 from the pylorus, through the gastric fistula, it was tightly embraced 

 from time to time, and drawn toward the pyloric orifice for a distance of 

 three or four inches. The object of this movement appears to be, as 

 just said, to carry the food toward the pylorus as fast as it is formed into 

 chyme, and to propel the chyme into the duodenum; the undigested 

 portions of food being kept back until they are also reduced into chyme, 

 or until all that is digestible has passed out. The action of these fibres 

 is often seen in the contracted state of the pyloric portion of the stom- 

 ach after death, when it alone is contracted and firm, while the cardiac 

 portion forms a dilated sac. Sometimes, by a predominant action of 

 strong circular fibres placed between the cardia and pylorus, the twopor- 



