168 DIGESTION. 



the gastric juice, which is at the same time poured out by the mucous 

 membrane ; so that the digestive fluid is made to penetrate equally 

 every part of the alimentary mass, and the digestion of all its albu- 

 minous ingredients goes on simultaneously. This movement of the 

 stomach is one which cannot be completely imitated in experiments on 

 artificial digestion with gastric juice in test-tubes ; and consequently the 

 process, under these circumstances, is never so rapid as when it takes 

 place in the interior of the stomach. 



The result of the action of the gastric juice, thus incorporated in the 

 stomach with the alimentary matters, is that they are disintegrated by 

 the softening and liquefaction of their albuminous ingredients. Bread 

 consists mainly of hydrated starch, entangled and incorporated with 

 the semi-solid gluten. By digestion in the stomach, the gluten is di- 

 gested and liquefied by its conversion into albuminose, the starch being 

 thus set free, and the whole reduced to a diffluent condition. The same 

 effect can be seen when bread is subjected to the action of gastric juice 

 in a test-tube, the gluten passing into the condition of liquid albuminose, 

 while a deposit of unaltered starch settles at the bottom. Cheese, con- 

 sisting of coagulated caseine and milk globules, undergoes an analogous 

 change. Its caseine is liquefied by digestion, while its liberated fat 

 globules rise to the upper part of the fluid, forming a creamy-looking 

 layer upon its surface. 



Adipose tissue is very readily disintegrated by the liquefaction of its 

 connective tissue, which is formed of albuminous matter, while the fatty 

 matter escapes in the form of oil drops, floating upon the surface of 

 the other contents of the stomach. Dr. Beaumont always found free 

 fat, in the form of oil globules, thus extricated from the fatty tissues 

 soon after they had been introduced into the stomach with the food ; 

 and it is easy to verify this observation, either by artificial digestion of 

 adipose tissue in gastric juice, or by opening the stomach of an animal 

 soon after the administration of food containing fat. 



The digestion of muscular flesh is also at first a process of disintegra- 

 tion. The connective tissue intervening between the fibrous bundles 

 yields to the action of the gastric juice, and the fibres themselves thus 

 become separated from each other, and form a gruelly mixture of minute 

 and almost microscopic threads and fragments. The substance of the 

 muscular fibres then also begins to become altered they break up into 

 shorter fragments, and, when examined by the microscope, are found to 

 have lost the distinctness of their transverse striations. If the food 

 have been thoroughly masticated before being taken into the stomach, 

 this change goes on rapidly and uniformly throughout the mass. If, 

 as in the dog, the meat be swallowed without much mastication, or if 

 portions be suspended in a test tube containing gastric juice, the action 

 progresses regularly from without inward. The external parts of the 

 muscular tissue are first softened and decolorized, and become covered 

 with a grayish layer, of grumous consistency, containing the isolated 

 and partially destroj^ed fragments of muscular fibre. As these por- 



