104 VETERINAEY HYGIENE 



question of digestibility will be dealt with later ; for 

 our present purpose it is sufficient to say that only a portion 

 of the proteid and non-nitrogenous substances in any diet 

 is capable of absorption, the remainder is excreted with the 

 fffices. 



The albuminoid ratio is calculated not on the total 

 amount of proteid and carbo-hydrate in the diet, but only 

 on that definite proportion which numerous experiments 

 have shown is capable of being extracted from it by the 

 system. The albuminoid ratio, then, is calculated on the 

 digestible constituents of a diet. 



The digestible constituents of a diet which have to be 

 considered are, proteid, fat, and carbo-hydrate. In the 

 latter is included not only the starch in the food, but all 

 the non-nitrogenous substances capable of digestion, viz., 

 sugar, gummy substances, cellulose, etc., which we have 

 previously said when absorbed have the same nutritive 

 value as starch. 



It will be borne in mind that the proteid of vegetable 

 tissues is made up of albumen proper and amides, the latter 

 being described in the table on p. 96 as non-albuminous 

 nitrogen. In calculating the amount of digestible proteid 

 in a diet, both of these are included, as in the present 

 state of our knowledge the real function of amides is not 

 accurately known. 



The fat is calculated as pure fat, though again it will be 

 remembered that excepting in cereals the fat is mainly of 

 the nature of wax, and has not the same value as pure fat. 

 The digestible fats in the diet are multiplied by the factor 

 2-44, by which factor the fat (calculated from the oxygen 

 required for its combustion) is converted into its equivalent 

 of starch. In other words, the fat is regarded as giving 

 nearly two and a half times more heat than starch. 

 Finally, all the remaining digestible non-nitrogenous con- 

 stituents are taken and regarded as equivalent to starch. 



We have now arrived at the necessary data for calcula- 

 ting the albuminoid ratio of any food or diet, viz., it is 

 only to be calculated upon the digestible portion of the 



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