288 DIGESTION. 



so completely closed, that even when the stomach is sepa- 

 rated from the intestines, none of its contents escape. But 

 towards the termination of the digestive process, the 

 pylorus seems to offer less resistance to the passage of 

 substances from the stomach ; first it yields to allow the 

 successively digested portions to go through it ; and then 

 it allows the transit of even undigested substances. 



From the observations of Dr. Beaumont on the man St. 

 Martin, it appears 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 

 approximated towards the pylorus. The movements were 

 observed to increase in rapidity as the process of chymifica- 

 tion advanced, and were continued until it was completed. 



The contraction of the fibres situated towards the pyloric 

 end of the stomach seems to be more energetic and more 

 decidedly peristaltic than those of the cardiac portion. 

 Thus, Dr. Beaumont found that when the bulb of the 

 thermometer was placed about three inches from the 

 pylorus, it was tightly embraced from time to time and 

 drawn towards 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 towards 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 stomach after death, when it alone is con- 

 tracted 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 two por- 

 tions, or ends as they are called, of the stomach, are separated 

 from each other by a kind of hour-glass contraction. 



The interesting researches of Dr. Brinton have clearly 

 established that, by means of this peristaltic action of the 



