GASTRIC TESTS. 81 



a test-meal should be given. This should be rather simple, and 

 may consist of bread or rolls with weak tea without milk. A 

 large amount of food rich in albuminous materials should be 

 avoided, as the peptones resulting from its digestion interfere with 

 some of the tests. With such a meal digestion is at its height in 

 about an hour, and the collection should be made one to one and 

 a half hours after eating. 



The apparatus for withdrawing the juice is an elastic rubber 

 tube about a yard in length, having a number of small perforations 

 in the end or, if a large opening, it should be on the side, to avoid 

 injury to the mucous membrane by suction. The perforated end 

 is passed slowly down the oesophagus until it reaches the fundus 

 of the stomach, known by the resistance to its further passage. 

 The flow of the juice through the siphon is best started by press- 

 ure upon the stomach, the outer end of the tube being held lower 

 than the stomach and over a collecting vessel. By this means the 

 juice is not diluted. 



Sometimes it is recommended to start the siphon by filling 

 it with water by means of a funnel, then when it is full, pinching 

 the top of the tube to close it and quickly lowering it. The first 

 part of the liquid which runs out is water and should be thrown 

 away, collecting only the last part. Otherwise the amounts of 

 constituents found must be corrected for the water, which dilutes 

 the juice. The addition of water, however, prevents accurate quan- 

 titative tests. 



Before testing the juice it should be filtered through a 

 plaited filter, keeping it covered to avoid loss of water or 

 acid by evaporation. 



The tests which are usually made upon the gastric 

 juice are for: 



1. Eeaction. 



2. Acid phosphates. 



3. Hydrochloric acid. 



(Lactic. 

 Butyric. 

 Acetic. 

 5. Pepsin. 



