COMPOSITION OF THE GASTRIC JUICE. 241 



of the gastric juice give the phosphate of lime as one of its constituents; and Blondlot 

 justly remarks that it is strange to see, in certain analyses, the neutral phosphate of lime 

 and hydrochloric or lactic acid put down as existing together, as though the phosphoric 

 acid were able to retain the two equivalents of the base in the presence of either of these 

 two acids. The fact is, that basic phosphate of lime, a salt insoluble in pure water but 

 soluble in acid solutions, is invariably decomposed in the presence of acids as powerful as 

 the hydrochloric or the lactic. It then loses two equivalents of the base and is trans- 

 formed into an acid phosphate. 



There can be no doubt of the constant presence of the acid phosphate of lime in the 

 gastric juice, at least in the dog, and its quantity is undoubtedly increased in this animal 

 during the digestion of bones, by the action of the acid fluid upon their phosphatic con- 

 stituents ; but the arguments of Blondlot against the existence of a free acid have little 

 or no weight. One of those on which most stress is laid is that the gastric juice does not 

 act upon the carbonates, which would undoubtedly be the case if it contained a free 

 acid. The simple reply to this is that there is sufficient evidence to show that it is 

 not the fact. Melsens, using a specimen of fluid obtained by Blondlot from the dog and 

 given to Dumas, found that seventy-three grammes of juice dissolved, in twenty-four 

 hours, 0-108 of a gramme of calcareous spar (crystallized carbonate of lime). He con- 

 firmed this observation by several experiments, so that there can be no doubt as to its 

 accuracy. 



It is plain, therefore, that, while the acid phosphate of lime has been shown to be a 

 constant constituent of the pure gastric juice, contributing, in a certain degree, to its 

 acidity, it is not by any means to be regarded as the sole acid principle ; the phosphate 

 probably existing in this form by virtue of the presence in this fluid of a free acid. 



On what does the acidity of the gastric juice depend? This is the simple question to 

 which the foregoing discussion naturally leads ; and it is one which can be answered 

 almost with positiveness, although it is not settled to the satisfaction of all physiologists 

 and there are some conflicting observations which can be harmonized only by new re- 

 searches. 



Aside from the conditions under which acids, such as butyric, acetic, or lactic, are 

 developed from articles of food taken into the stomach, the evidence is strongly in 

 favor of free lactic acid as the principle on which the gastric juice mainly and constantly 

 depends for its acidity. There also exists a certain quantity of biphosphate of lime; and 

 this is the only condition in which a phosphate of lime can exist in the presence of free 

 lactic acid. 



The observations of Bidder and Schmidt indicate, apparently, a quantity of chlorine 

 in the gastric juice not to be accounted for by the proportion of bases obtained by ulti- 

 mate analysis. There is evidence sufficiently positive to show that there is no hydro- 

 chloric acid in the gastric juice, in a condition which allows the fluid to present the re- 

 actions which are observed when this acid exists in a free state. If there be any hydro- 

 chloric acid not in combination with metallic bases, it is united with organic matter in 

 such a way as to prevent the manifestations of its ordinary properties, except that of 

 acidity. The fact that some of the mineral acids can be made to unite in this way with 

 albuminoid substances lends color to this supposition ; although farther investigations 

 are necessary to demonstrate that this takes place in the gastric juice. 



Ordinary Saline Constituents of the Gastric Juice. It has been experimentally de- 

 monstrated that artificial fluids, containing the organic principle of the gastric juice and 

 the proper proportion of free acid, are endowed with all the digestive properties of the 

 normal secretion from the stomach, and that these properties are rather impaired when 

 an excess of its normal saline constituents is added or when the relation of the salts to 

 the water is disturbed by concentration. Boudault and Corvisart evaporated two hun- 

 dred grammes of the gastric juice of the dog to dryness and added to the residue fifty 

 16 



