IN THE HEALTHY STOMACH. 113 



lius 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, Braconnet 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 enclosing air in the shape of 

 froth, in a far higher degree than even soap-suds. 

 This air, by means of the saliva, reaches the stomach 

 with the food, and there its oxygen enters into com- 

 bination, while its nitrogen is given out through the 

 skin and lungs. The longer digestion continues, that 

 is, the greater the resistance offered to the solvent 

 action by the food, the more saliva, and consequently 

 the more air enters the stomach. Rumination, in 



