STOMACH AND INTESTINE. 



373 



has no higher solvent power over albuminous 

 substances than that possessed by the similar 

 fluid prepared from pieces of ileum or colon. 

 While the strongly acid reaction of its contents 

 in many herbivorous animals is sufficiently 

 explained as due to that lactic fermentation, 

 which the various starchy substances are so 

 apt to undergo when exposed to spontaneous 

 decomposition at the temperature (about * 

 103) of the intestinal canal. Consistently with 

 such an explanation, this acid reaction is found 

 chiefly or exclusively in those parts of the 

 faecal mass which are not in contact with 

 the alkaline mucous membrane, and is by 

 no means limited to the contents of the coecal 

 pouch. 



We may therefore regard the faeces as com- 

 posed chiefly of two constituents : which 

 are derived, the one from the food taken by 

 the animal, and the other, from the secretions 

 of its digestive organs. And in like manner, 

 we may premise what follows by stating, 

 that the composition of any particular excre- 

 ment will always depend on the nature of the 

 food, the state of the secretions, and the na- 

 ture and amount of the metamorphoses which 

 both these constituents have together under- 

 gone. 



Physical properties of the faces Subject to 

 circumstances so numerous and fluctuating, it 

 is obvious that the physical properties of the 

 faeces must vary extremely in different sub- 

 jects. Their ordinary colour, odour, form, 

 size, and consistence are so well known, as 

 scarcely to require any special description in 

 this essay. 



As regards the two first of these characters, 

 the contents of the small intestine are dis- 

 tinctly faecal. But it is only in the ccecum, 

 where both their colour and odour become 

 much more marked, that the fasces usually 

 begin to acquire a solid consistence. Their 

 form and size is dictated, partly by the 

 shape and diameter of the bowel (as already 

 alluded f to), and partly by the degree in which 

 their consistence has been augmented by the 

 absorption of their watery parts. Where 

 their solidity is much increased from this 

 latter cause, the act of expulsion has little 

 influence in modifying their form. The way 

 in which it usually does this has been 

 previously pointed out. 



The odour and colour peculiar to the faeces 

 have been ascribed, by some authors, to the 

 bile which enters into their composition ; by 

 others, to the fluids which are poured out 

 into the intestinal canal from the blood-vessels 

 occupying its mucous membrane. It is, how- 

 ever, probable that they are not due to either 

 of these causes exclusively, but depend rather 

 on a combination of both; and are further mo- 

 dified by that admixture of altered (not to say 

 decomposing) food, which forms so large a 

 constituent of the excrement. 



Thus, that they depend to some extent on 

 the bile, is well shown by those cases of 



* Brown Se'qtiard, " Experimental Researches in 

 Physiology and Pathology," New York, 1853. 

 t See p. 366. 



jaundice, in which a deficient secretion of this 

 fluid, or an obstruction of its normal channel, 

 has arrested its flow into the intestine. For 

 in such instances, the ordinary brownish yel- 

 low tint, and faecal smell, proper to the excre- 

 ment, are exchanged for a greyish white co- 

 lour, and an intensely putrefactive odour. 



But it is certain that, unless the bile be 

 poured out in excessive amount (as after the 

 exhibition of mercury *), or conveyed through 

 the bowels with unusual rapidity (as in diarrhoea 

 and purging), it is but a small fraction of its 

 total quantity that escapes re-absorption, so as 

 to be found in the faeces. This statement 

 especially applies to the meconium which 

 occupies the intestine of the foetus. At any 

 rate, this substance contains but little of the 

 acid or the colouring matter of ordinary bile. 



Now, the preparation of excrement by the 

 fcetus, and by hybernating or starving animals, 

 is a satisfactory proof that its specific faecal 

 characters are not essentially due to any modifi- 

 cation of the alimentary matters contained in 

 the intestinal canal. And since the bile forms 

 but a small portion of its mass, it is evident 

 that much of it must be derived from the se- 

 cretions of the digestive tube itself, and that its 

 properties must be partially due to the same 

 source. Indeed, this intestinal constituent, 

 which is probably always a large ingredient 

 of the faeces, becomes, in the hybernant and 

 the fcetus by far the largest : so much so, 

 that the dried meconium contains about 85 

 to 95 per cent, of epithelium and mucus, al- 

 most all of which must be referred to this 

 source. While, as regards its physiological 

 import, it is impossible to doubt that it is 

 (/cor' foY/)c) the excrement : that it is, in fact, 

 the chief excretory ingredient of the faeces ; 

 and hence that ingredient, the dismissal of 

 which from the intestinal canal is most essen- 

 tial to the welfare of the organism generally. 



The above view, as to the share which both 

 the biliary and the intestinal constituents take 

 in producing the colour and odour of the 

 faeces, appears so irrefragable, that we may 

 content ourselves with a passing allusion to 

 those experiments by which it has been at- 

 tempted to establish the predominant or exclu- 

 sive influence of either. Thus, while it has 

 been pointed out by Valentin f that putre- 

 fying bile diffuses the strongest smell of or- 

 dure, LiebigJ states that he has succeeded in 

 the artificial production of the fascal odour by 

 a process which essentially consists in imper- 

 fectly oxidizing some of the more azotized tis- 

 sues of the body. The latter experiment has 

 been regarded as leading to the inference, that 



* The green colour of the stools after calomel has 

 been taken seems to be due, partly to the chemical 

 reaction of the contents of the intestine, partly to 

 an increase in the quantity of bile poured out. The 

 latter fact has been continued by experiments, in 

 which this drug has been administered to dogs pro- 

 vided with biliary fistulas opening externally. The 

 chemical change undergone by the mercury in the 

 intestinal tube consists (like that of the salts of 

 iron under similar circumstances) in the formation 

 of a sulphuret of the metal. 



t Lehrbiich der f'hysiologie, vol. i., p. 370. 



j Animal Ch& fftry, 3rd ed., p. 148. et seq. 



I! IJ 3 



