108 GASTRIC JUICE. 



chemists who have examined that fluid since. This 

 muriatic acid is obviously derived from common salt, 

 the soda of which plays a very decided part in the con- 

 version of fibrine and caseine into blood. 



Muriatic acid yields to no other acid in the power of 

 dissolving bone earth, and even acetic acid, in this re- 

 spect, is equal to lactic acid. There is consequently 

 no proof of the necessity of lactic acid in the digestive 

 process ; and we know with certainty, that in artificial 

 digestion it is not formed. Berzelius, indeed, has found 

 lactic acid in the blood and flesh of animals ; but when 

 his experiments were made, chemists were ignorant of 

 the extraordinary facility and rapidity with which this 

 acid is formed from a number of substances containing 

 its elements, when in contact with animal matter. 



In the gastric juice of a dog, Braconnot found, along 

 with free muriatic acid, distinct traces of a salt of iron, 

 which he at first held to be an accidental admixture. 

 But in the gastric juice of a second dog, collected with 

 the utmost care, the iron was again found. (Ann. de 

 Ch. et de Ph. lix. p. 249.) This occurrence of iron 

 is full of significance in regard to the formation of the 

 blood. 



12. In the action of the gastric juice on the food, no 

 other element takes a share, except the oxygen of the 

 atmosphere and the elements of water. This oxygen 

 is introduced directly into the stomach. During the 

 mastication of the food, there is secreted into the mouth 

 from organs specially destined to this function, a fluid, 

 the saliva, which possesses the remarkable property of 



