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HANDBOOK OF PHYSIOLOGY. 



gases contained in the alimentary canal, and those present in the blood 

 of these gastric and intestinal blood-vessels; but the conditions of the 

 exchange are not known, and it is very doubtful whether anything like 

 a true and definite secretion of gas from the blood into the intestines or 

 stomach ever takes place. There can be no doubt, however, that the 

 intestines may be the proper excretory organs for many odorous and 

 other substances, either absorbed from the air taken into the lungs in 

 inspiration, or absorbed in the upper part of the alimentary canal, again 

 to be excreted at a portion of the same tract lower down in either ease 

 assuming rapidly a gaseous form after their excretion, and in this way, 

 perhaps, obtaining a more ready egress from the body. It is probable 

 that, under ordinary circumstances, the gases of the stomach and intes- 

 tines are derived chiefly from the second of the sources which have been 

 enumerated. 



Composition of Gases of the Alimentary Canal. 



(Tabulated from various authorities by Brinton.) 



The above table differs little from the average obtained by more 

 modern observers, but it emits an important point to which attention 

 should be drawn, viz., that the amounts of the gases vary with the diet. 

 For all practical purposes oxygen and sulphuretted hydrogen may be 

 omitted. An analysis of the intestinal gases (Ruge, copied by Hallibur- 

 ton) in man is as follows: 



Sources of the Carbon Dioxide. From the carbonates and lactates in 

 food; from alcoholic fermentation of sugar; from putrefaction of car- 

 bohydrates and proteids; and from butyric acid fermentation. 



Sources of the Hydrogen. From butyric acid fermentations of lactic 

 acid 



