Nutrition. 235 



animal ; a sheep, for instance, digests hay better than a 

 horse, and this digestion is not limited, as one might 

 expect, to the cellulose only, but is extended to the other 

 proximate principles, excepting the proteids, of which both 

 animals digested the same amount. 



The following table will show the average percentage of 

 each proximate principle digested by animals. The figures 

 are the means of a mixed diet : 



Albuminoids 

 Fatty matter 

 Carbo-hydrates 

 Cellulose and fibre 



By laborious experiments, the digestive co-efficient of all 

 the principal feeding stuffs has been obtained. The subject 

 cannot here be dealt with further ; a full account is given 

 elsewhere.* 



It is evident that every food, no matter how well- 

 balanced in its proximate principles, will contain a certain 

 proportion of digestible and indigestible matter ; the latter, 

 no doubt, largely depends upon the presence of cellulose 

 and lignin. The herbivora, though adapted to digest these, 

 cannot obtain from their food the full amount of nutriment 

 if either of them be in great excess ; but apart from 

 this no food is fully digested : there is a certain proportion 

 of proteid, fat, sugar, and cellulose which the animal can- 

 not extract or assimilate from the total amount given it. 

 This is a point of practical importance. 



The digestibility of a food is affected by its Nutritive 

 Relation, and this term we must now explain. The nutritive 

 relation of a food is : (1) the proportion which the proteids 

 bear to the fat and carbo-hydrates, minus the cellulose ; 

 (2) the proportion of fats to the nitrogenous principles ; 

 and (3) the proportion of nitrogenous or proteid principles 

 to the whole of the non-nitrogenous. The first is called 

 the nitrogenous ratio ; the second the fatty ; the third the 

 complete nutritive ratio. By splitting up food into these 

 * ' Veterinary Hygiene.' 



