GASTRIC TESTS. 91 



to each specimens of natural or artificial gastric juice, con- 

 taining different amounts of pepsin, including one with 

 none. If they are not sufficiently acid make them so. Set 

 the tubes in a beaker of water of about body-temperature 

 and notice the setting free of the color as the pepsin acts. 



The rennin is detected by neutralizing and testing 

 with milk for the power of coagulation as in Experiment 

 190. 



The test for starch and its first decomposition-product, 

 dextrin, is iodin dissolved in potassium iodid. According 

 to von Jaksch, neither of these remains in the stomach in 

 normal digestion after the first hour, though they may be 

 present as long as as that when there is an excess of acid or 

 deficiency of ptyalin in the saliva. 



The albuminous substances and digestive products can 

 be detected by the methods given in Experiments 185, 186, 

 and 187, and by the tests described for albuminous com- 

 pounds. 



The gastric juice never normally contains blood, but 

 this is sometimes found in it or in the vomited material in 

 cases of chronic ulceration of the stomach or after poison- 

 ing by the corrosive or strongly irritant poisons. The 

 haemoglobin is usually decomposed and the haamatin which 

 results gives a dark-brown color, to the juice. It is best 

 identified by the hasmin test (Experiment 253). 



It is occasionally desired to test the rapidity of absorption 

 from the stomach. This can be accomplished by determining how 

 long a time is necessary for potassium iodid to pass from the 

 stomach through the circulatory system into the saliva. About 

 5 grains of the iodid is taken in a capsule or in water, in the 

 latter case being careful to thoroughly rinse the mouth afterward, 

 latter case care being taken to thoroughly rinse the mouth after- 

 ward. The saliva is collected and tested every minute after the 



