STOMACH AND INTESTINE. 



377 



circulates in the capillaries of the organ. 

 And this diffusion probably imitates that which 

 takes place between the air and the blood at 

 the surface of the lungs and skin. It will 

 therefore convert the gaseous mixture of the 

 atmosphere into one containing less oxygen, 

 and more carbonic acid ; the extent of the 

 change in both these respects varying chiefly 

 with the duration of its sojourn in the stomach. 



But a number of circumstances unite to 

 prove that the gases of the stomach are in 

 great part derived from some other source. 

 Thus the quantity of air taken with the food 

 can be but small. \Vhile percussion and aus- 

 cultation show, that the cavity of the healthy 

 organ is often largely distended with gas. And 

 the above analysis further points out, that not 

 only is the increase of carbonic acid dispro- 

 portionate to the decrease of oxygen, and 

 therefore (unlike the interchange in the skin 

 and lungs) not due to a mere physical pro- 

 cess of diffusion, but that a new element, 

 hydrogen, has been added to it. 



The same arguments apply still more for- 

 cibly to those gases, which almost invariably 

 distend the intestines. For during diges- 

 tion, they could hardly pass the pylorus; and 

 at any other time, would be very unlikely to 

 enter the stomach, through which alone they 

 could reach the duodenum. Hence in the case 

 of the intestinal segments of the canal, we 

 are referred almost exclusively to those sources 

 which, we have already seen, will be necessary 

 to explain the greater part of the gas present 

 in the stomach. 



2. Gases may be developed in the alimen- 

 tary canal from the decomposition of the food 

 which it contains. 



Difficult as it is to decide on the evidence 

 at present before us, there seem to be valid 

 reasons for regarding this as the process by 

 which theintestinal gases are chiefly, if not ex- 

 clusively, set free in the alimentary cavity. 

 The food introduced into this cavity is speedily 

 converted into a decomposing mass, which is 

 useful to the organism solelv by virtue of the 

 metamorphoses it is undergoing. And though 

 these metamorphoses generally seem to be 

 limited to processes, by which elements are 

 merely re-arranged in the solid or liquid form, 

 and not given off as gases, still they are easily 

 susceptible of being carried further, so as to 

 involve a more or less copious evolution of 

 gaseous fluids. 



Now, the putrefaction of the protein com- 

 pounds of the food, together with the fermen- 

 tation of its hydrates of carbon, would amply 

 account for these gases; as well as for the 

 ammonia which has been alluded to as pro- 

 bably throwing down part of the soluble 

 phosphates of the intestinal contents, in the 

 form of crystals of the triple phosphate of am- 

 monia and magnesia. For not only are all the 

 gases in the above analyses producible by the 

 various processes of putrefaction external to 

 the body, but their proportions to each other 

 are precisely those which might be expected 

 from the known composition of the food. 



The conditions which favour the presence 



of these gases remarkably confirm this view. 

 Too large a quantity of food and especially 

 of food that consists of substances which are 

 either putrefying or fermenting, or are pecu- 

 liarly liable to undergo these changes noto- 

 riously increases the amount of gases thus 

 generated in the bowels. The liability of 

 cattle to a dangerous distention of this kind, 

 when surfeited with green food, is well known 

 to agriculturists. And in like manner, an 

 increased quantity of sulphuretted hydrogen 

 is generally expelled in the flatus of animals 

 which have been fed upon* beans, or made to 

 take sulphur with their food. While the 

 practice of medicine acquaints us with the 

 fact, that all circumstances which lower the 

 tone of the alimentary canal, or lessen the 

 energy of its secretions, further these sponta- 

 neous (though abnormal), metamorphoses of 

 its contents ; and thus give rise to a corres- 

 ponding increase in the quantity of the gases 

 which form their direct result. We may per- 

 haps find an additional confirmation of this 

 view in a comparison of the various instances 

 analyzed above. At least, the great devia- 

 tions which they exhibit, seern better expli- 

 cable by the variable composition of the food, 

 than by any theory which would refer their 

 development to the organism or the blood 

 itself. 



Finally, it is well known that the complete 

 exclusion of food from the digestive cavity 

 often gives rise to a peculiar white and con- 

 tracted state of the tube, which implies an 

 entire absence of all such gaseous contents 

 from the greater part of its length. This 

 appearance is so generally seen in the bodies 

 of animals after long fasting, as to constitute 

 an important feature in the medico-legal evi- 

 dence of death by starvation. 



3. It has been supposed that gases are set 

 free in the intestinal canal by a kind of secre- 

 tion or transpiration from the blood. 



But in alluding such a process, it is neces- 

 sary to premise that, strictly speaking, it 

 would hardly deserve the name of a secretory 

 act. Even assuming that it really discharged 

 the gases of the blood into the intestinal canal, 

 we should scarcely be warranted in terming 

 their passage a true process of secretion. 

 On the contrary, all analogy indicates that it 

 would rather constitute an act of diffusion : 

 a diffusion which would probably obey the 

 same laws, and exhibit somewhat of the same 

 course, as that which chemistry has success- 

 fully investigated in the case of the lungs and 

 skin. 



In any case, unless we suppose the capil- 

 laries of the intestine to be the actual site of an 

 unexampled generation of gas from the con- 

 stituents of the blood, an inquiry into these 

 latter will probably afford us some grounds 

 on which to accept or reject the above theory. 



It is therefore important to point out, that 

 some of the gases found in these analyses 

 viz. hydrogen, carburetted hydrogen, and sul- 



* The legumeu of which contains much of this 

 element. 



