CHAP. XXIV.] THE GASTRIC JUICE. 201 



horse, calf, and dog. And he announced, as the result of his 

 analyses, " that free or at least unsaturated muriatic acid in no 

 small quantity exists in the stomach of those animals during the 

 digestive process." And in later publications Dr. Prout has 

 reasserted this statement. 



The weight which is so deservedly attached to the opinion of 

 this eminent philosopher has, no doubt, had great influence in deter- 

 mining the prevalent opinion in this country in favour of the view 

 which attributes the acidity of the gastric fluid to the existence of 

 free muriatic acid in it. The source of the acid, it is generally 

 believed, is the chloride of sodium of the blood, which at the 

 mucous membrane of the stomach contributes muriatic or hydro- 

 chloric acid to the gastric juice, leaving free soda to be carried to 

 the liver by the veins of the stomach. 



Experiment, however, shows that muriatic acid has little or no 

 solvent power on the food, and that the reducing action of the 

 gastric fluid cannot be attributed to it alone. Albumen or meat 

 subjected to the action of water acidulated with muriatic acid, and 

 kept for some hours at a temperature of 100, undergoes no change of 

 any importance : neither substance exhibits any softening or ten- 

 dency to putrefaction or decomposition of any kind. Similar experi- 

 ments with acetic acid or with phosphoric acid lead to like results. 



It is plain, then, that the solvent powers of the gastric fluid are 

 not due simply to the acid which it contains, whatever that may 

 be, and that we must look for some other ingredient in it, which, 

 either alone or in combination with acid, can exercise these powers. 

 The clue to this was given by Eberle, who adopted the expedient of 

 adding to water acidulated with muriatic acid a small piece of the 

 mucous membrane of the stomach. By this means he succeeded 

 in obtaining a digestive fluid which reduced animal substances as 

 perfectly as the gastric juice itself. 



This discovery was of the last importance to the formation of a 

 correct theory of stomach digestion, and to exact views of the 

 nature of the gastric juice. It was soon followed up by numerous 

 experiments in Germany by Schwann and Miiller, and by Purkinje 

 and Pappenheim. The general result of these experiments was, 

 that the addition of a portion of gastric mucous membrane from the 

 true secreting stomach to an acidulated water produced a perfect 

 digestive fluid; but that no other mucous membrane would answer 

 this purpose. The following changes take place on macerating 

 meat and albumen in a digestive fluid: The meat is broken 

 down to a complete pulp; and, if the digestion have been con- 



VOL. II. P 



