ACTION OF THE GASTEIC JUICE IN DIGESTION. 253 



tral phosphate of lime and adding acetic, phosphoric, or 

 hydrochloric acid, in such quantity that it certainly existed 

 in a free state, the digestive properties of the fluid were re- 

 tained. These authors regard it as essential that the normal 

 acid of the gastric juice should be thus capable of being 

 replaced indifferently by other acids; for, they say, in 

 case any salt were introduced into the stomach which would 

 be decomposed by the lactic acid of the gastric juice, diges- 

 tion would be interfered with, unless the liberated acid 

 could take its place. 1 It can readily be appreciated that 

 transient disturbances might occur from this cause were the 

 .existence of any one acid principle indispensable to the di- 

 gestive properties of the gastric juice ; while if only a certain 

 degree of acidity were required, this condition might be pro- 

 duced by any acid, either derived from the food or produced 

 by secretion. 



Enough has already been said under the head of the or- 

 ganic principle of the gastric juice to show that the presence 

 of this substance is likewise a condition indispensable to 

 digestion. 



The necessity of an acid and an organic principle in the 

 gastric juice can be shown by the following simple experi- 

 ment, which we have often made use of as a class-demon- 

 stration : Take three cubes of coagulated white of egg, one 

 of which is put into pure gastric juice, the other into gastric 

 juice which has been carefully neutralized, and the third 

 into gastric juice in which the properties of the organic prin- 

 ciple have been destroyed by boiling. If the three speci- 

 mens be kept at about the temperature of the body for a 

 number of hours, the albumen in the pure juice will be 

 found to be partially or completely reduced to a grumous 

 consistence, readily breaking up between the fingers, while 

 the other specimens are scarcely acted upon. 



As far as has been ascertained by experiments in artificial 

 digestion, the mucus, which always exists in greater or less 



1 Op. dt. Comptes Rendus, Pari?, 1844, tome xix., p. 1289. 



