SECTION XI 

 THE PIECES 



THE fseces 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 fseces, in fact, are not derived from the food, but are produced 

 almost entirely in the alimentary canal itself. This is shown by the fact 

 that on analysing the fseces no soluble carbohydrates or proteins, albu- 

 moses, 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 fseces 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 fseces. Under these circumstances the fseces 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, 

 dy sly sin, 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 fseces contain about 0-11 grm. of purine bases per diem, 



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