72 THE GASTRIC JUICE. 



phates are present in the normal juice. The lactic acid 

 may be found in the first stages of digestion, especially 

 when the food contains much of the carbohydrates, but 

 is not normally found after digestion has proceeded more 

 than half an hour. The acetic and butyric acids are not 

 normally present. 



The free hydrochloric acid appears to be formed from 

 the chlorids which are taken with the food. Its forma- 

 tion has been explained as due to the action of disodium 

 phosphate upon calcium chlorid and also to the decomposi- 

 tion of sodium chlorid by a weak acid, like carbonic acid. 

 Neither explanation, however, is perfectly satisfactory. A 

 free acid is necessary for the digestion of the nitrogenous 

 foods by the pepsin, and this is one of the offices of the 

 hydrochloric acid. Recent researches have indicated that 

 one of its most important functions is the prevention of 

 fermentation in the stomach. The mineral acids have 

 antiseptic powers even in such dilution as that of the hy- 

 drochloric acid in the gastric juice; that is, from 0.2 to 

 0.3 per cent. Such a solution will, for several days, pre- 

 vent putrefaction in animal matter, like chopped meat, 

 which would otherwise soon commence to decay. It will 

 also destroy the bacteria of many infectious diseases, 

 though some of these are not affected when in the form 

 of spores. 



The effects of increased fermentation are seen in cer- 

 tain pathological conditions where the secretion of hydro- 

 chloric acid is diminished or stopped. They are especially 

 noticeable in the case of food containing large quantities 

 of carbohydrates. The sugar which is formed by the saliva 

 may be changed by the ferments into different acids: 



C 6 H 12 6 2C 3 H 6 3 . 



cuoel sS lactic acid 



