THE "RERPTTIATION OALOKTMETEK. 



1047 



to sinipl}^ state the a^'el•ag•G composition of the protein and fat of cat- 

 tle, from whicli that of other .species differs l)ut sliuhtly. 



According- to this conception the effect of a ration is expressed by 

 the gain or loss of ash, protein, fat, and, of course, water, by the 

 body of the animal, and this gain or loss may be determined by com- 

 paring the amounts of ash, nitrogen, and carbon in the food with those 

 contained in the various excreta, solid, liquid, and gaseous; that is, 

 by a so-called balance experiment. As regards ash, the method is suf- 

 ficiently obvious, and the principal interest centers in the methods for 

 the organic ingredients, viz, protein and fat. 



Since the term protein, as above used, is synonymous with total nitrog- 

 enous matter, the gain or loss of protein ma}" be determined by a 

 comparison of the income and outgo of nitrogen. Furthermore, since 

 the vast majority of physiologists regard it as demonstrated that there 

 is no material excretion of gaseous nitrogen by the bod}^ we may con- 

 fine the determinations of nitrogen to the food and the visible excreta. 

 For example, in two experiments with a steer, in which the rations 

 consisted, respectively, of 4,531 grams and 5,750 grams of timothy 

 hay, with the addition in each case of 400 grams of linseed meal, the 

 following figures for daily nitrogen were obtained as the average of 

 a ten-day period following a preliminary period of eleven days: 



Nitroge)! balance in two x>t'rio(U of a feeding ex2)eriment with a steer. 



Period A. Period B. 



Nitrogen in hay 



Nitrogen in linseed meal 



Nitrogen, total in feed.. 

 Nitrogen in feces 



Nitrogen digested 



Nitrogen in urine 



Nitrogen in hair, etc 



Lo.ss of nitrogen by body 



1.2 



In Period A the outgo of nitrogen is shown to have exceeded the 

 income b}" 8.2 grams. Multiplying this by the factor 6.0 (correspond- 

 ing to 16. C7 per cent nitrogen) we tind that in this period the steer 



