548 SPECIAL PHYSIOLOGY. 



[The experiments by the editor upon Alexis St. Martin, referred to 

 in the note on page 529, confirm the statements here made as to the 

 office of the gastric juice in digesting albuminous articles of food, by 

 a previous conversion into alburninose or peptones. So, also, that 

 gastric juice has no effect upon oleaginous food other than to liberate 

 the oil by dissolving away the albuminous envelopes of the fat-vesicles. 



With regard to amylaceous constituents of food, these experiments 

 upon St. Martin, as well as others more recently performed through 

 the kindness of Dr. E. Brown- Sequard, who, it will be remembered, 

 has the faculty of vomiting at will, showed distinctly the presence of 

 grape-sugar in the products of gastric digestion, as determined by 

 Trommer's test; and this in much larger quantity than could be ob- 

 tained by the action of saliva for the same length of time upon a por- 

 tion of the same arrowroot swallowed by Brown-Sequard, and which 

 had been previously tested for glucose without the response usual 

 when this substance is present. That the glucose thus found in the 

 products of gastric digestion is the result of the action of gastric juice 

 upon the amylaceous food is not contended for. The change has 

 been most probably produced by the action of the mucus secreted by 

 the mucous follicles of the stomach, as it is well known that mucus 

 from any mucous membrane has this effect. Thus, an injection of 

 starch in the rectum, when evacuated, is found to respond to Trom- 

 mer's test for grape-sugar. (North American Med.-Chir. Rev., July, 

 1857, and Jour, de Physiologic, Jan. 1858.) F. G. S.] 



The agent by which the gastric juice dissolves, or excites the solu- 

 tion of albuminoid and gelatinoid substances, is the peculiar animal 

 substance, itself albuminoid, the pepsin; but the free acid contained in 

 it is also essential to the digestive process. Dilute hydrochloric, or 

 other acid, of the strength of that present in the gastric juice, possesses 

 by itself no digestive property, though it renders the tissues semi-trans- 

 parent, and dissolves out earthy matter from bones. Again, pepsin 

 alone, obtained pure by precipitation from the gastric juice by means 

 of alcohol, filtration, and re-solution in water, also possesses no diges- 

 tive power; nor does pure gastric juice, provided that its acid be care- 

 fully neutralized; for small pieces of meat, or albumen, placed in such 

 solutions, do not digest, but after a time putrefy. 



These, and many other facts, concerning the rapidity and results of 

 digestion, have been established by experiments, amongst the most in- 

 teresting in Physiology, on artificial digestion, i. e., by subjecting dif- 

 ferent substances to the action of different digestive fluids, under ex- 

 actly like conditions. The temperature employed may vary from 96 

 to 102. During natural digestion, the temperature of the stomach of 

 Alexis St. Martin, was found to be from 100 to 101 F. ; whilst 

 during fasting, it was 98 or 99. (Dr. F. G. Smith.) 



An artificial digestive fluid may be obtained directly from the human 

 or animal stomach, by first exciting the flow of gastric juice, and then 

 causing vomiting; or it may be collected from artificial gastric fistulas 

 in animals. A digestive fluid may, however, be more conveniently, 

 and less cruelly, obtained from the gastric mucous membrane of the re- 



