220 METHODS FOR THE ANALYSIS OF GASTRIC JUICE 



Calculation. Note the number of cubic centimeters of N/100 

 sodium thiosulphate required to titrate 1 c.c. of stomach contents 

 to the total disappearance of blue color in the presence of starch. 

 Inasmuch as N/100 thiosulphate is equivalent to N/100 alkali, 

 this value indicates the number of cubic centimeters of N/100 

 sodium hydroxide necessary to neutralize the free hydrochloric 

 acid in 1 c.c. of the stomach contents. Multiply the value by 10 

 to obtain the number of cubic centimeters of N/10 NaOH necessary 

 to neutralize 100 c.c. of stomach contents. 



(c) Determination of Peptic Activity. (1) Method of Mett as 

 Modified by Nirenstein and Schiff. Principle. Small glass tubes 

 filled with coagulated egg albumin are introduced into the solution 

 to be tested, and kept for a definite length of time in the incubator. 

 The protein column is digested at both ends of the tube to an 

 extent depending upon the amount of pepsin present. The 

 method is not strictly accurate but is the most satisfactory for 

 clinical purposes on account of its simplicity. Nirenstein and 

 Schiff showed that human gastric juice contained inhibiting sub- 

 stances the effect of which is overcome by the dilution recom- 

 mended. 



Procedure. Introduce into a small Erlenmeyer flask 1 c.c. 

 of gastric juice and 15 c.c. of N/20 HC1 ( = 0.18 per cent HC1). 

 Add two Mett tubes prepared as indicated below, stopper the 

 flask to prevent evaporation and place in an incubator at 37 C. 

 for twenty-four hours. By means of a low-power microscope and 

 a millimeter scale (graduated to half millimeters) determine 

 accurately the length of the column of albumin digested at each 

 end of the tubes. It is well to run the determination in duplicate, 

 in which case the result is the average of the eight figures obtained. 

 Ordinarily from 2 to 4 mm. of albumin are digested by normal 

 human gastric juice. 



Calculation. The peptic power is expressed as the square 

 of the number of millimeters of albumin digested. This is based 

 on the Schiitz-Borissow law that the amount of proteolytic enzyme 

 present in a digestion mixture is proportional to the square of the 

 number of millimeters of albumin digested. Therefore a gastric 

 juice which digests 2 mm. of albumin contains four times as much 

 pepsin as one which digests only 1 mm. of albumin. 



Example. If the microscopic reading gives on an average 

 2.2 mm. of albumin digested the pepsin value for the diluted 



