PHYSIOLOGICAL 105 



and the daily average quantity of faeces is 30 lb., but may' be 

 double as much. With cattle the amount is still greater, and 

 averages 75 lb. The sheep and pig discharge about 4 lb. of 

 faeces daily. 



"Animals living on a mixed animal and vegetable diet, like 

 man, pass daily about 130 grammes of faeces, containing 

 34 grammes of solids, which will represent about 5 per cent, 

 of the solids taken as food. When the vegetable diet is in excess, 

 this may rise to 13 per cent., so that only seven-eighths of the 

 solids are finally absorbed. ... In a man fed on a milk and 

 meat diet only 2j to 10 per cent, escapes in the faeces; with a 

 vegetable diet, rice, bread and potatoes, the loss may amount 

 to 30 per cent., though the carbohydrates are almost completely 

 absorbed, only i per cent, being lost, and only 5 per cent, of 

 fats escapes absorption." 



An examination of the urine of different classes of animals 

 is in certain respects equally suggestive. Thus in man, indican 

 though often present is not a normal constituent of the urine, 

 but is regarded as evidence of "indigestion" or incomplete 

 metabolism. But in the horse or ox indican is invariably to 

 be found in the urine and often in considerable quantity. 



It is, of course, incontestable that the nutritive habits of 

 animals can be changed under artificial or unusual conditions, 

 that many Carnivora can be got to subsist on a purely vegetable 

 diet, and that herbivorous animals may be induced to feed upon 

 fish or even upon flesh, food-substances for which their denti- 

 tion is entirely unsuited. Moreover, by cooking the food and 

 thus rendering it softer and reducing it to a condition in which 

 the digestive fluids can play upon it more freely, and such that 

 the undigested residue can be more easily passed onwards by 

 the peristaltic movements of the gut wall, the disadvantages of 

 an abnormal diet may be reduced. Nevertheless, when animals 

 fed in an unusual way are given the chance of returning to their 

 natural food they almost invariably do so. 



This is not the place, even if space permitted, for a general 

 treatment of the fundamental principles on which a rational 

 system of feeding must be based, but enough has been said to 

 show that the consideration of a dietary is not merely a matter 



