COMPOUNDING RATIONS 235 



proportions can, therefore, be found by comparing the N-ratios 

 of the foods with that of the dietary. 



Now take the actual case of linseed cake and rice meal 

 as before. The differences between the ratios are 



6 2*24 = 3*76 and 6 10*83 = 4*83 



If the foods contained the same percentages of protein 

 they should be taken in that proportion, i.e. 376 parts of rice 

 meal to 4*83 of cake, or 0773 of the former to i of the latter. 

 As, however, the cake contains 4-16 times as much protein 

 as the rice [0*773 X 4*16 =] 3*24 parts of rice should be 

 taken to i of cake. The whole calculation may be briefly 

 rendered thus 



(6 2*24) X 25 _ 376 X 25 _ 3^4 

 (10-83 6)X 6~ 4*83 X 6 "' i 



Protein. "Starch." 



Lb. Lbs. 



3-24 Ibs. Rice contain 0*194 2*106 



i -oo ,, Cake , 0*250 0-560 



.... 0*444 2*666 



4*24 X 10 3*24 



~ 



0*444 4*24 



The reasoning in the above calculation is rather involved, 

 but it may be illustrated by simple graphic methods. 



Graphic Solutions. If the percentages of protein and 

 " starch" be plotted on the axes ox and oy (Fig. 15), a line 

 ON can be drawn to represent the ratio of the dietary (6 to i), 

 and two others, OL and OR representing the N-ratios of the 

 cake (2*24 to i) and of the rice (10*83 to *) respectively. If, 

 now, a straight line AE be drawn to cut these ratio lines, the 

 two portions, AD and DE, will represent the difference between 

 the N-ratios of the foods and that of the dietary. Through 

 D draw CG at right angles to AE, and cut off DC equal to 

 the percentage of protein in the cake, and DG equal to the 

 percentage in the rice ; the areas of the completed rectangles, 



