COMPARATIVE DIGESTIBILITY OF FOOD-STUFFS. 435 



of albuminous matters being greater in the green than in the dry fodder, 

 even though of the same material ; while still further the statement 

 may be made that the larger the relative proportion of albuminous matter 

 and the smaller the amount of the cellulose, the greater will be the amount 

 of albuminous matter digested. 



Fifth. The digestive co-efficient of the different food-stuffs may be 

 altered through the addition to the food of different nutritive substances. 

 Thus, it has been shown that the administration of a readily digestible 

 albuminous diet is without influence on the co-efficient of digestion of 

 the other foods; but, on the other hand, the addition of starch or sugar 

 will reduce the digestive co-efficient of the albuminous bodies when the 

 amount of carbohydrates given exceeds by 15 per cent, the solids of the 

 other food-stuffs. This depression of digestibility is especially marked 

 in the dry foods. A similar result is also manifested when beets and pota- 

 toes are added. The addition of oil is without influence on the digestive 

 co-efficient so long as it is not given in great amounts. When the amount 

 given exceeds the proportion of one-tenth gramme to one kilogramme of 

 body weight, slight disturbances of digestibility are readily produced. 

 When the food is composed of several nutritive substances combined, 

 the proportion of the nitrogenous and the non-nitrogenous constituents 

 of the total amount is of great influence on the digestibility. This 

 nutritive relationship of the non-nitrogenous substances is found by 

 adding the amount of fat to the sum of the non-nitrogenous extractive 

 matters, the amount of cellulose being excluded. Ordinarily the amount 

 of fat is multiplied by two and four-tenths or two and five-tenths, and 

 this product then added to the amount of extractive matters, — a pro- 

 cedure which is, however, apt to give an erroneous idea as to the nutri- 

 tive value of the fat. 



The general result may be stated that a food is readily digestible 

 when the proportion between nitrogenous and non-nitrogenous con- 

 stituents varies from 1 : 5 to 1 : 1. An increase of this proportion causes 

 a certain amount of the n on -nitrogenous constituents to remain undi- 

 gested while an increase of the nitrogenous substances causes a waste. 

 It is evident that the above statement as to the digestibility of food may 

 be only regarded as in general true. Each group of animals will possess 

 special facilities for digesting special foods ; these will deserve considera- 

 tion in turn. 



As might be expected, the time required for undigested food to 

 appear as faeces after feeding very closely corresponds in different 

 animals with the comparative length of the intestinal canal. Thus, it 

 has been found that in oxen fed with oat-straw the first traces appear in 

 the faeces about thirtj'-six hours after feeding, and disappear after seventy- 

 two to ninety-six hours, while in the goat seven days were required after 



