SECTION X 

 THE FAECES 



THE faeces are often regarded as representing the undigested or indigestible 

 constituents of the food which have escaped solution and absorption in their 

 passage through the alimentary canal. This view is hardly correct as applied 

 to man or to the carnivora. In these the absorption of the constituents of 

 a meal, whether consisting of fats, proteins, or carbohydrates, is practically 

 complete by the time that the food has arrived at the lower end of the 

 ileum. The faeces, in fact, are not derived from the food, but are produced in 

 the alimentary canal itself. This is shown by the fact that on analysing 

 the faeces no soluble carbohydrates or proteins, albumoses, peptones, or 

 amino-acids are to be found. After a meal of meat microscopic examination 

 of the faeces reveals no trace of striated muscle fibres. Moreover animals 

 in a state of complete starvation form faeces which do not differ in their 

 composition from the faeces which are found after feeding with meat, eggs, 

 sugar, or cooked starch, though the amount is less in a state of inanition than 

 under normal circumstances. In one experiment Hermann isolated a loop 

 of gut, joining its ends together so that a continuous ring was formed. The 

 continuity of the gut was then restored by suturing the two free ends. After 

 some weeks the isolated loop was found to contain a semi-solid material 

 similar to faeces in appearance, consistence, and chemical composition. It 

 contained a large amount of phosphoric acid, lime, and iron. 



So long as vegetables or coarsely ground cereals are excluded from the 

 diet, the nature of the latter does not alter the chemical constitution or 

 appearance of the faeces. Under these circumstances the faeces have the 

 following composition : 



Water . . . . 65 to 67 per cent. 

 Nitrogen . . . . 5 to 9 



Ether extract . . . 12 to 18 ,. 



Ash 11 to 22 



The ash consists chiefly of lime and phosphoric acid with some iron and 

 magnesia. The ethereal extract contains fatty acids and a small amount 

 of lecithin. Neutral fat is present in very small proportions. The faeces also 

 contain small quantities of cholalic acid and its products of decomposition, 

 dyslysin, and coprosterin, a body allied to cholesterin, and a certain amount 

 of purine bases consisting of guanine, adenine, xanthine, and hypoxanthine. 

 On the average the faeces contain about 0-11 grm. of purine bases per diem, 



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