288 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



proper time and the contents of its stomach being collected. A better method 

 of obtaining normal juice was suggested by the famous observations of Beau- 

 mont 1 upon Alexis St. Martin. St. Martin, by the premature discharge of 

 his gun, was wounded in the abdomen and stomach. On healing, a fistulous 

 opening remained in the abdominal wall, leading into the stomach, so that the 

 contents of the latter could be inspected. Beaumont made numerous interest- 

 ing and most valuable observations upon his patient. Since that time it has 

 become customary to make fistulous openings into the stomachs of dogs when- 

 ever it is necessary to have the normal juice for examination. A silver canula 

 is placed in the fistula, and at any time the plug closing the canula may be 

 removed and gastric juice be obtained. In some cases the oesophagus has 

 been occluded or excised so as to prevent the mixture of saliva with the gastric 

 juice. Gastric juice may be obtained from human beings also in cases of vom- 

 iting or by means of the stomach-pump, but in such cases it is necessarily 

 more or less diluted or mixed with food and cannot be used for exact analyses, 

 although specimens of gastric juice obtained by these methods are valuable in 

 the diagnosis and treatment of gastric troubles. 



Properties and Composition of Gastric Juice. — The normal gastric secre- 

 tion is a thin, colorless or nearly colorless liquid with a strong acid reaction 

 and a characteristic odor. Its specific gravity varies, but it is never great, 

 the average being about 1002 to 1003. Upon analysis the gastric juice is 

 found to contain a trace of proteid, probably a peptone, some mucin, and 

 inorganic salts, but the essential constituents are an acid (HC1) and two 

 enzymes, pepsin and rennin. A satisfactory analysis of the human juice has 

 not been reported, owing to the difficulty of getting proper specimens. 

 According to Schmidt, 2 the gastric juice of dogs, free from saliva, has the 

 following composition, given in 1000 parts : 



Water 973.0 



Solids 27.0 



Organic substances 17.1 



Free HC1 3.1 



NaCl 2.5 



CaCl, 0.6 



KC1 LI 



NII 4 C1 0.5 



Ca3(P0 4 ) 2 1-7 



Mg,,fP0 4 ) 2 0.2 



FeP0 4 0.1 



Gastric juice docs not give acoagulum upon boiling, but the digestive enzymes 

 are thereby destroyed. One of the interesting facts about this secretion is the 

 way in which it withstands putrefaction. It may be kept for a long time, for 

 months even, without becoming putrid and with very little change, if any, in 

 its digestive action or in its total acidity. This fact shows that the juice 

 possesses antiseptic properties, and it is usually supposed that the presence of 

 the free acid accounts for this quality. 



1 Tlte Phmi'ihujii of Digestion, 1833. 



2 Hammarsten: Text-book of Physiological Chemistry translated by Mandel), 1893, p. 177. 



