CHAP. XII.] 



THE FAECES IN HEALTH. 



457 



though the amount of meat consumed varied between 500 and 2500 grms. 

 Under these cgnditions, the faeces are almost black, tenacious like pitch or 

 simply solid and are only evacuated at intervals of some days. On a diet 

 of bread, defecation occurs at least once daily, and the weight of faeces ex- 

 creted is much greater than on a flesh diet, reaching one-sixth to one-eighth 

 of the weight of the food ingested. Thus in Bischoff and Yoit's first set of 

 experiments, the amount of bread consumed per diem amounted to 857 

 grms., which corresponded to 460 grms. of water-free bread. The faeces 

 weighed 377 grms. and contained 76 grms. of solid matters, so that for 

 every 100 grms. of bread consumed, there were excreted 16 '6 grms. of 

 faeces. Faeces passed on a purely bread diet are of a yellowish-brown and 

 crumble easily. They possess a strongly acid reaction and are coloured of 

 an intense blue by iodine. The percentage composition of these faeces, 

 compared with that of bread, shews that they are composed of nearly 

 unchanged bread which the digestive apparatus has been unable to utilise, 

 whilst the faeces passed on a flesh diet differ widely in composition from 

 flesh, as the subjoined table will shew 1 . 



Results of Observations on the Dog (Bischoff and Voit}. 



Reaction of We have drawn attention to the almost universally 



propagated error that the contents of the small in- 

 testine usually possess an alkaline reaction. We have now to em- 

 phasize the parallel error which is also widely diffused, viz. that 

 the contents of the large intestine and the faeces possess an acid 

 reaction. The exact contrary is true. Usually the normal faeces of 

 man are alkaline, and it is very exceptional that they present an 

 acid reaction. 



The odour of 

 the faeces. 



The specific foul odour of faeces is due to indol 

 and especially to skatol, developed by the action of 

 putrefactive bacteria in the colon. Occasionally, sulphuretted hydro- 

 gen, ammonia, and other volatile bases, contribute to the foetid odour. 



1 This account of Bischoff and Voit's experiments (Die Gesetze der Erndhrung des 

 Fleischfressers, Leipzig u. Heidelberg, 1860, p. 290) is taken from the paper by 

 Macfadyen, Nencki and Sieber, Archiv f. exp. Path. u. Pharm., Vol. xxvm. (1891), 

 p. 344. 



