348 



PHYSIOLOGY 



CHAP. 



Euge analysed the intestinal gases of man, as given off per 

 anurn, with the following results : 



C. S. Hofmann never detected methane or marsh gas in his 

 work on the intestinal gases of dogs and rabbits, but hydrogen 

 was constantly present, with traces of oxygen and sulphuric acid. 



As shown by the tables, carbonic acid always occurs in large 

 quantities, particularly after a vegetable diet. It may be developed 

 by different processes, by cleavage of the alimentary carbonates, 

 lactates, acetates, and citrates ; by alcoholic fermentation of glucose; 

 by putrefaction of carbohydrates (particularly of cellulose) and 

 proteins; by butyric fermentation of lactic acid; lastly by 

 diffusion from the capillaries of the mucous membrane of the 

 intestine. 



The hydrogen, which is present in large quantities, especially 

 in a milk diet, is undoubtedly due to the butyric fermentation of 

 lactic acid, during which carbonic acid and hydrogen are developed. 



The methane, which is developed in man in large quantities 

 after a diet of meat and vegetables, while it is scanty in a milk 

 diet, originates in the decomposition of acetates and lactates 

 (Hoppe-Seyler) and of cellulose (Hoppe-Seyler, Tappeiuer, Henne- 

 berg, and Stohmann) ; also to a small extent from the decomposi- 

 tion of the choline, derived from lecithin. It is difficult to explain 

 the absence of methane in the intestinal gases of the dog and 

 rabbit. 



Nitrogen is always present, though it varies much in quantity 

 with different diets. For the most part it comes from the 

 swallowed air, left behind after absorption of the oxygen ; it may 

 arise partly, however, from diffusion through the wall of the intes- 

 tine (Bunge), and also from putrefaction of the proteins, with 

 simultaneous development of ammonia. 



The sulphuric acid, of which traces are normally present in the 

 intestinal gases, originates undoubtedly in the putrefaction of 

 proteins, during which ammonia, sulphuric acid, ammonium 

 sulphate, fatty acids, amines and amino-acids (especially leucine 

 and tyrosine), and aromatic ethers (particularly indole, scatole, 

 phenol, and cresol) are developed. 



