DIGESTION. 155 



The following is the composition of the gastric juice of the dog, 

 based on a comparison of analyses by Lehmann, Blondlot, Otto, and 

 Bidder and Schmidt. 



COMPOSITION OF GASTRIC JUICE. 



Water 975.00 



Free acid 4.78 



Pepsine 15.00 



Sodium chloride 1.70 



Potassium " ' 1.08 



Calcium " 0.20 



Ammonium " 0.65 



Lime phosphate 1.48 



Muirnesium " 0.06 



Iron " 0.05 



1000.00 



Schmidt, in the case which fell under his observation, found the gas- 

 tric juice of man similar in constitution to the above, except that it 

 contained a larger proportion of water and a smaller proportion of free 

 acid and pepsine, as well as of solid ingredients generally. In the case 

 investigated by Richet, the amount of acid was, on the average, 1.7 

 per thousand parts, its minimum being 0.5 and its maximum 3.2. 

 Such differences may therefore exist between individuals, or even in 

 the same individual at different times ; depending no doubt on the 

 more or less rapid secretion of the watery parts. Observations on 

 the dog show that the proportion of solid ingredients is usually less 

 when the secretion is abundant, and greater when it is in small quan- 

 tity. In either case the essential constituents are the same. 



The most striking physical property of the gastric juice is its acid 

 reaction, by which it is distinguished from all the other digestive secre- 

 tions and internal fluids of the body. This property depends on the 

 presence of its free acid. Notwithstanding that all observers have 

 recognized in the gastric juice a distinct acidity, a singular difference 

 of opinion still exists as to the particular body which gives it this 

 reaction, and especially whether it be a mineral or an organic acid. 

 Repeated analyses have been made by different methods, and each 

 new result has been claimed as decisive on the one side or the other. 

 Many observers (Front, Dunglison, Enderlin, Schmidt, Ewald, Hoppe- 

 Seyler) regard the free acid of the gastric juice as hydrochloric acid. 

 Their conclusion is mainly based on the fact that the total quantity of 

 hydrochloric acid obtainable from the secretion is more than sufficient 

 to saturate all the alkaline and earthy bases which it contains. Others 

 (Lehmann, Leuret and Lassaigne, F. G. Smith, Laborde, Bernard and 

 Barreswil) consider the acid ingredient to be lactic acid. In support 

 of this view they adduce certain reactions of the gastric juice which 

 do not belong to solutions of hydrochloric acid, such as precipitation 

 of lime oxalate on the addition of a little oxalic acid,* and the fact that 



* Bernard. Leyons de Physiologic Experimentale. Paris, 1856, p. 396. 



