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 fa3ces 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 fa3ces which do not differ in their composition from the fasces 

 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, con- 

 sistence, 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 



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