THE GASTKIC JUICE AND STOMACH DIGESTION. 169 



tions are removed by the peristaltic movements of the stomach, the 

 digestive action extends to the parts underneath, and so on until the 

 whole has been reduced to a uniform mixture, of a thickish gruelly con- 

 sistency, in which the distinctive elements of the tissue are no longer 

 recognizable by the eye, and in which the remnants of the muscular 

 fibres can only be detected by the microscope. It, is this apparently 

 homogeneous, pultaceousor gruelly semi-fluid material that was formerly 

 designated by the name of "Chyme." It is evidently nothing more 

 than a mixture of the disintegrated remnants of the digested tissues, 

 portions of which have been completely liquefied while others are not 

 yet reduced to a state of solution. 



When milk is taken into the stomach in a fresh condition, its caseine 

 is at first coagulated, afterward dissolved. The preliminary coagula- 

 tion, which is due to the action of the pepsine and dilute acid, takes 

 place very rapidly. Dr. Beaumont found that milk could be withdrawn 

 in a coagulated condition in fifteen minutes after its introduction into 

 the stomach ; and that if the mixture were kept at the temperature of 

 38 (100 F.), the coagula were again liquefied in the course of eight 

 hours. The coagulation of milk, thus produced by its first contact 

 with the gastric juice is, however, no obstacle to its subsequent diges- 

 tion. The caseine does not form a solid uniform clot, but is thrown 

 down in the form of minute flocculi, of soft consistency, which are 

 constantly bathed by the digestive fluids, and at the temperature of the 

 living body undergo readily the conversion into albuminose. As it is 

 this chemical change which constitutes the real process of digestion, 

 the preliminary coagulation of the caseine does not interfere with its 

 accomplishment. Milk, furthermore, as used by adults, is to a large 

 extent incorporated, in the coagulated form, with other solid or semi- 

 solid articles of food. 



The substance of vegetable tissues, as a rule, is digested in a similar 

 manner to that described above. The albuminous matters are dissolved 

 out, leaving the starchy or oleaginous ingredients in a free condition, 

 but chemically unchanged. As these tissues generally contain a much 

 smaller proportion of albuminous matter than most kinds of animal 

 food, their disintegration is the main result of the changes which they 

 undergo in the stomach. 



The gastric juice, together with the disintegrated debris of the food, 

 after commencing its action in the stomach, passes into the upper part 

 of the intestine. This can be seen readily in the dog by killing the 

 animal after feeding, and examining the contents of the intestine. We 

 have observed the same thing by establishing, in the dog, an artificial 

 duodenal fistula, by means of an operation similar to that for producing 

 a permanent fistula of the stomach. A silver tube, armed at each 

 end with narrow projecting flanges, is introduced into the lower part 

 of the duodenum, and the wound allowed to heal, after which the 

 contents of the intestine may be withdrawn at will, and subjected to 

 examination at different periods during digestion. 

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