222 GASTEIC DIGESTION. 



Boudault and Corvisart evaporated 6'76 oz. (200 c. c.) of the gastric juice of 

 the dog to dryness and added to the residue, 1'69 oz. (50 c. c.) of water. They 

 found that the fluid thus prepared, containing four times the normal propor- 

 tion of saline constituents, did not possess by any means the energy of action 

 on alimentary substances of the normal secretion. These facts have led 

 physiologists to attach little importance to the saline constituents of the gas- 

 tric juice, except sodium chloride, which is thought to be concerned in the 

 production of hydrochloric acid. 



Action of the Gastric Juice in Digestion. Certain of the substances most 

 readily attacked by the gastric juice are acted upon by weak, acid solutions 

 containing no organic matter ; but it is now well established that the presence 

 of a peculiar organic matter is a condition indispensable to actual diges- 

 tion. It has also been shown that fluids containing the organic constituent 

 of the gastric juice have no digestive properties unless they also possess the 

 proper degree of acidity ; and it is as well settled that fluids containing acids 

 alone have no action on albuminoids similar to that which takes place in 

 digestion, and that when these substances are dissolved by them it is simply 

 accidental. 



The presence of any one particular acid does not seem essential to the 

 digestive properties of the gastric juice, so long as the proper degree of acidity 

 is preserved, and it is undoubtedly important that the normal acid can be re- 

 placed by other acids ; for in case any salt were introduced into the stomach 

 which would be decomposed by the acid of the gastric juice, digestion would 

 be interfered with, unless the liberated acid could take its place. It can 

 readily be appreciated that transient disturbances might occur from this 

 cause, were the existence of any one acid indispensable to the digestive prop- 

 erties of the gastric juice ; while if only a certain degree of acidity were re- 

 quired, this condition might be produced by any acid, either derived from the 

 food or secreted by the stomach. 



In studying the physiological action of the gastric juice, it must always be 

 borne in mind that the general process of digestion is accomplished by the 

 combined as well as the successive action of the different digestive fluids. 

 The act should be viewed in its ensemble, rather than as a process consisting 

 of several successive and distinct operations, in which different classes of ali- 

 mentary matters are dissolved by distinct fluids. The food meets with the 

 gastric juice, after having become impregnated with a large quantity of 

 saliva ; and it passes from the stomach to be acted upon by the intestinal 

 fluids, having imbibed both saliva and gastric juice. 



When the acts which take place in the mouth are properly performed, the 

 following alimentary substances, comminuted by the action of the teeth and 

 thoroughly insalivated, are taken into the stomach : muscular tissue, contain- 

 ing the muscular substance enveloped in its sarcolemma, blood-vessels, nerves, 

 ordinary fibrous tissue holding the muscular fibres together, interstitial fat, 

 and a small quantity of albuminoids and corpuscles from the blood, all com- 

 bined with a considerable quantity of inorganic salts ; albumen, sometimes 

 unchanged, but generally in a more or less perfectly coagulated condition ; 



