1 8 PHYSIOLOGICAL CHEMISTRY. 



tube add a section of a Mett tube 1 and place the mixture at 38 C. 

 for ten hours. At the end of this period, the tube should be re- 

 moved from the gastric juice and the length of the column of 

 coagulated albumin which has been digested, carefully determined 

 by means of a low power microscope and a millimeter scale. In 

 normal human gastric juice the upper limit is 4 mm. However, 

 control tests should always be made to determine the digestibility 

 of the coagulated albumin in artificial gastric juice inasmuch as 

 this factor will vary with different albumin preparations. 



In connection with this test Schiitz's law should be borne in 

 mind. This principle is to the effect 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 a gastric juice which digests only i mm. of albu- 

 min. And further, if the quantities of albumin digested are 2 mm. 

 and 3 mm. respectively, the ratio between the pepsin values will 

 be as 4 : 9. 



It is claimed by Nirenstein and Schiff that the principle of 

 Schiitz does not apply to gastric juice unless this fluid be diluted 

 with fifteen volumes of N/2O hydrochloric acid. 



(b) Fuld and Levison's Method. This test is founded upon 

 the fact, shown by Osborne, that edestin when brought into solu- 

 tion in dilute acid will change in its solubility, due to the contact 

 with the acid, and that a protean called edestan, which is insoluble 

 in neutral fluid, will be formed. The procedure is as follows: 

 Dilute the gastric juice under examination with 20 volumes of 

 water and introduce gradually decreasing volumes of the diluted 

 juice into a series 2 of narrow test-tubes about i cm. in diameter. 



1 In the preparation of these tubes, egg-white is .diluted with an equal volume 

 of water, the precipitated globulin filtered off and the filtrate collected in a 

 tall, narrow beaker or a large test-tube. A bundle of capillary tubes about 10 

 cm. in length and 2 mm. in diameter are now placed in this vessel in such a 

 manner that they are completely submerged in the albumin solution. After an 

 examination has shown that the tubes are completely filled with the albumin 

 solution and that there are no interfering air-bubbles, the vessel and its con- 

 tained tubes is. heated for 5-15 minutes in a boiling water-bath, in order to 

 coagulate the albumin. When this coagulation is complete, the tubes are re- 

 moved, all albumin adhering to them is carefully cleaned off, and the tubes 

 rendered air-tight by the application of sealing wax at either end. When 

 needed for use, these tubes are cut into sections about 2 cm. in length. 



* The longer the series, the more accurate the deductions which may be drawn. 



