154 



PHYSIOLOGICAL CHEMISTRY 



substantiated by experiments made in the author's laboratory 1 and 

 elsewhere. 2 Both bile and trypsin are easily identified in the stomach 

 contents of man after the introduction of 0.5 per cent hydrochloric 

 acid into the empty organ. The above points are illustrated by the 

 chart shown in Fig. 49, page I53. 3 



The composition of human gastric juice and of the residuum (see 

 page 163) is given in the following table: 



COMPOSITION OF HUMAN GASTRIC JUICE 



THE USE OF INDICATORS IN DETERMINING THE REACTION OF GASTRIC 

 JUICE AND OTHER FLUIDS 



The reaction of the gastric juice and other body fluids is most 

 readily tested by means of indicators, so-called because they show 

 changes of color with differing degrees of acidity or alkalinity of the 

 solution. They behave as though they were weak acids or bases whose 

 ions and unionized molecules have different colors. Modern theories 

 of color in organic compounds however class them as tautomeric 

 substances. 



A neutral solution is one in which there are equal numbers of hy- 



1 Spencer, Meyer, Rehfuss and Hawk: Am. Jour. PhysioL, 39, 459, 1916. 

 2 Migai: Diss., St. Petersburg, 1909. 



MUosorov: Zent. PhysioL, 28, 615, 1914. 



Zaitzeff: Russky Vrach., 14, No. 29, 1915. 

 'Spencer et al: LOG. cit. 

 4 Carlson : LOG. cit. 



6 Fowler, Rehfuss and Hawk: LOG. cit. 

 Fowler & Buchanan: Unpublished. 



