DIGESTION 251 



that which the stomach absorbs most readily, which 

 explains to some extent the rapidity with which it exerts 

 its effects. Peptone, sugar, and salts are also absorbed 

 to some degree. On the other hand, water, curiously 

 enough, is scarcely absorbed at all. Hence, in pyloric 

 stenosis the tissues may suffer from water starvation 

 unless water be administered by other routes e.g., the 

 rectum. 



There is reason to believe that the process of absorp- 

 tion by the stomach partakes much more of the nature 

 of a mere physical osmosis than is the case in the 

 intestine, and it is accompanied by the pouring out of a 

 good deal of secretion. It is in this way, perhaps, that 

 a mixture of alcohol and sugar, such as is found in 

 sweet wines and malt liquors, may cause ' acidity.' 



The Gases of the Stomach. 



The stomach usually contains a small amount of 

 gas, which consists of a mixture of nitrogen and COg? 

 the latter being present in the same proportion as 

 oxygen in atmospheric air, whilst the nitrogen is present 

 in the same proportion as it is in air. It is believed that 

 the nitrogen is derived from swallowed air, the oxygen 

 of which has been absorbed by the bloodvessels of the 

 gastric mucous membrane, whilst the nitrogen escapes 

 absorption because the blood is saturated with it already. 

 The CO 2 is probably transfused from the blood. Evans* 

 has brought forward evidence, derived from a study of 

 the gas contained in the swim-bladder of fish, in favour 



^ Brit. Med. Journ., 1897, i. 649. 



