THE GASTRIC JUICE. 217 



has the property of dissolving albuminoid substances, does 

 not during life destroy the coats of the organ which secretes it. 



It appears that certain insoluble metallic salts are acted 

 upon by the acids of the gastric juice, and reduced to a state 

 of solution. By some it has been supposed that calomel, 

 which is an insoluble chloride of mercury, is dissolved by 

 the chlorides of the gastric juice. Iron, when taken into the 

 stomach, is reduced to the state of oxide at the expense of 

 the water contained in that organ. It is evident that this 

 solvent action is dependent on the gastric juice, as it is 

 most active during the period of digestion. Cyanide of 

 mercury is a salt very easily decomposed by the gastric juice, 

 and its poisonous properties seem to depend on the hydro- 

 cyanic acid thus set free; and Bernard has observed that 

 symptoms of poisoning ensue most rapidly if it be taken 

 during digestion. We have seen that, if an alkali be added to 

 gastric juice out of the body, the property of digesting nitro- 

 genous substances is destroyed. The same, however, does not 

 happen in the body; for it is found that the alkali seems to 

 act as a stimulus to the secretion of gastric juice. 



John Hunter observed that, after death, the coats of the 

 stomach often undergo a process of solution by the gastric 

 juice; and for a long time physiologists were at a loss to ex- 

 plain the immunity which the stomach enjoys during 

 life. It has now been shown that the stomach owes this pro- 

 perty to the continually renewed epithelium of its mucus coat ; 

 and that it is not dependent simply on the vitality of the 

 tissues, has been shown by some experiments of Claude Ber- 

 nard, who, having introduced the hind-legs of a frog through 

 a gastric fistula into the stomach of a dog, observed that they 

 were digested whilst the frog was still living. Thus it is 

 that, as science advances, many phenomena formerly consi- 

 dered to be vital (i.e., phenomena occurring in living beings, 



