376 



STOMACH AND INTESTINE. 



absorption of lime than magnesia in the intes- 

 tinal canal. Carbonates of the alkalies are 

 found in the ash of human excrement ; but 

 they are apparently almost absent from that 

 of the Sheep, Cow, and Horse. They are pro- 

 bably produced by a combustion of some or- 

 ganic salts of these bases. 



The elementary analyses of the faeces hither- 

 to made possess little physiological signifi- 

 cance, or general validity. But from what has 

 already been stated, it is obvious that the 

 entire excretory part of the ordure removes 

 from the body very little water or nitro- 

 gen ; probably not more than g^th or ^th of 

 that quantity of each of these elements which 

 is daily excreted in the urine. 



The time during which the contents of the 

 intestinal tube sojourn in its different segments 

 is probably a very uncertain as well as variable 

 one. In diarrhoea, the whole canal is some- 

 times traversed by these contents in two 

 hours ; while in obstruction, weeks or months 

 may elapse without their complete transit. 

 The mean rate which lies between these 

 two morbid states can only be conjectured. 

 But there are reasons for supposing, that 

 the food of a healthy adult occupies about 

 twelve hours in passing through the small 

 intestine. While from thirty-six to sixty hours 

 may be assumed as its average sojourn in the 

 large intestine, prior to its ultimate expulsion 

 from the rectum. 



Intestinal gases. In speaking of the elastic 



fluids which are generally contained in the 

 large intestine, and are occasionally expelled 

 from its lower orifice, it will be advantageous 

 to contrast them with the gases found in 

 other parts of the alimentary canal : viz., 

 in the stomach and the small intestine. Many 

 years ago the composition of these gaseous 

 contents of the canal was correctly given by 

 Jurine, from an examination of the corpse of 

 an idiot soon after death by cold. But it is 

 to Magendie* and Chevreul that we owe the 

 only trustworthy quantitative analyses on the 

 subject. Their observations were made upon 

 the gases found in the bodies of criminals im- 

 mediately after their execution. Some authors 

 have therefore thought it worth while to al- 

 lude to their results, as being probably affected 

 by the dyspepsia which the dread of such an 

 impending doom might be supposed to have 

 produced in these unhappy persons. With- 

 out, however, assigning any definite value to 

 this contingency, it is enough to say that they 

 still remain far preferable to any other such 

 analyses: to those, for instance, of Chevilloff", 

 whose rather different results are quite ex- 

 plained by the time after death to which his 

 examinations were deferred, and the decom- 

 position which had therefore begun, both in 

 the tissues of these corpses, and in the ali- 

 mentary and secretory contents of their in- 

 testines. 



We may best arrange these analyses in the 

 following tabulated form : 



It is only from such analyses that we can 

 form any reasonable inference as to the origin 

 of the gases to which they refer. 



In making such an inquiry, four sources 

 of aeriform matter at once suggest themselves ; 

 either of which seems at first sight capable of 

 at least partially explaining the presence of 

 gaseous substances in the digestive canal. And 

 the claims of each of these must be separately 

 examined before we can conjecture the proba- 

 ble amount of its product, or its share in those 

 reactions which the physical properties of 

 gaseous fluids so easily allow them to excite. 



1. Air may be introduced into the intestinal 

 canal from without the body. Just as some of 

 the lower animals can distend the abdomen 

 by a voluntary deglutition of air, while even 

 the higher Mammalia have been noticed to 

 fill the stomach with air by the movements 

 which precede the act of vomiting, so per- 

 sons have been observed to swallow air, and 



afterwards expel it by eructation. And apart 

 from such exceptional cases, there is good 

 reason for believing that the ingestion of food 

 always introduces into the stomach an ap- 

 preciable quantity of atmospheric air ; part of 

 which is perhaps mechanically carried down 

 with the alimentary bolus, while another part 

 enters the organ in a state of more minute di- 

 vision, with the frothy saliva. 



The air which is thus introduced into the 

 stomach will doubtless here undergo a certain 

 amount of diffusion or interchange with the 

 elastic fluids dissolved in the liquid blood that 



* Precis Elementaire de Physiologic, vol. ii., 

 p. 113. 



f Chevillot's figures (Berzelius' Jahresbericht 

 der physischen Wissenschaften, 1831, p. 247) indi- 

 cate that, in the diseased and decomposing bodies he 

 examined, oxygen was always present ; and carbonic 

 acid rather increased ; while the nitrogen sometimes 

 reached the large proportion of 99 per cent. 



