550 SPECIAL PHYSIOLOGY. 



ture of 120 A strongly acid artificial gastric juice is better suited 

 for the digestion of some substances, such as coagulated albumen, the 

 solid syntonin of cooked muscle, and legumin; whilst fibrin is more 

 quickly dissolved in a feebly acid juice, even 1 drop to 1 oz. of fluid. 

 (Bru'cke.) The strongly acid natural gastric juice of the Carnivora 

 acts most quickly on the firmer animal albumen, but the less acid se- 

 cretion of the Herbivora, most quickly on the softer vegetable gluten. 

 The human gastric juice has a feebler power even than that of the 

 herbivora; its acidity declares itself immediately on the introduction 

 of food into the stomach, and increases, for a time, as digestion goes 

 on, when the less digestible food requires to be attacked; when the 

 stomach is empty, the acidity quite disappears. 



The power of the gastric juice to dissolve animal substances is well 

 illustrated by the softening or digestion of the coats of the stomach by 

 its own secretion, after death, often noticed both in men and animals 

 dying whilst digestion is going on: all the coats of the stomach may 

 be thus perforated ; in the human body, the effects may simulate the 

 action of a corrosive poison. 



The immunity of the living gastric mucous membrane, or its power 

 of resisting the solvent action of its own secretion, has been variously 

 explained. According to one view, the epithelium and mucus consti- 

 tute a sufficient protection; for when the former is detached, the sub- 

 jacent tissue is said to be attacked, in the living stomach, as well as 

 after death. The "vitality " of the mucous membrane (the sum of its 

 vital actions), has been supposed to enable it to resist solution; and 

 this resistance necessarily ceases on the death of the part. A more 

 recent view, founded on many experiments, attributes the non-solution 

 of the living mucous membrane, to the protecting influence of the blood 

 in the capillaries, which is supposed to maintain, so long as the circu- 

 lation continues, the alkalinity of the tissues, a chemical condition 

 incompatible, as we have seen, with peptic digestion. (Pavy.) 



The digestive action of the fluids of the living stomach was shown 

 long ago by Spallanzani, Stevens, Tiedemann, Gmelin, and others, 

 who induced dogs to swallow pieces of sponge fastened to strings, and 

 afterwards withdrawing them, obtained a quantity of fresh gastric 

 iuice, which slowly dissolved food kept in it at a temperature of 100. 

 But the most direct evidence of the solvent power of gastric juice, is 

 that obtained by Dr. Beaumont, who employed the fluid collected from 

 the stomach of the Canadian voyageur, Alexis St. Martin. With that 

 fluid, the process of solution was very rapid. Three drachms of boiled 

 beef placed in an ounce of fluid, maintained at a temperature of 100, 

 began to digest in 40 minutes; in 60 minutes a pulpy deposit began to 

 form ; in 2 hours, the areolar tissue was digested, leaving the muscular 

 fibres disconnected or loosened: in 6 hours, these were nearly all di- 

 gested; and in 10 hours, the meat was completely dissolved; the gastric 

 juice, from being transparent, was now the color of whey, and contained 

 a meat-colored sediment. Digestion was still more rapidly accom- 

 plished, when a similar piece of beef, attached to a thread, was placed 

 in Alexis St. Martin's stomach ; for, although at the end of one hour, 

 its condition appeared much the same as that of the piece of beef di- 



