242 



FOODS AND DIETARIES 



Observations. 1. Two or more foods may be plotted as 

 follows : The combination, if equal in calorie value, is rep- 

 resented by a point midway between them. If the portions 

 are unequal, the point will of course be proportionally nearer 



the point locating the 

 larger portion. Like- 

 wise, when three foods 

 are combined, the point 

 is first located for two, 

 then this with the third, 

 this with the fourth, etc. 

 Thus in Figure 57 we 

 have three points repre- 

 senting respectively 300, 

 400, and 500 calories of 

 three separate foods. 

 We first join any two 

 points as 300 and 400, 



and find their combina- 

 FIG. 57. -Food map. Showing method of tion of 7Q Q ca l or i es at 

 combining three or more foods. (After . . . 



Fisher) the point 700 which 



divides the line joining 



the 300 and 400, as 3 to 4 and nearer the 400. We now unite 

 this with the 500 and find a new result at the point 1200. It 

 is now evident any number of portions may be thus combined, 

 the final number obtained equaling the sum of the portions, 

 and its location representing its value as a food. What is the 

 percentage composition of the combination of foods represented 

 by the figure 1200 ? Note. If the lines OF and CP are used 

 to compute the percentage of proteid and fat, how can you get 

 the percentage of carbohydrate ? 



2. Professor Chittenden believes that, of each 100 calories 

 used, 10 should be proteid, 30 should be fat, and 60 carbo- 

 hydrate. Locate this combination on a food map. Does it 

 fall within the rectangle wxyz, in Figure 58? Note. The 

 rectangle wxyz is known as the normal rectangle, and shows 



