23 



given in the following tables were obtained by multiplying the total num. 

 ber of grams of digestible protein by the factor 1.25, deducting the 

 amount got in this way from the calories representing the fuel value of 

 the digested portion of the food, dividing this by the number of calories 

 of heat got from the total food and multiplying by 100. This gives the 

 per cent, of the total energy of the food which is available to the body, or 

 the co-efficient of availability of the food. 



To -calculate the digestibility of the breakfast food alone, it is neces- 

 sary to know the digestibility of the several nutrients contained in the 

 tood fed with it. It will be remembered that cream and sugar only were 

 eaten with the cereal. As the digestibility of these has been determined 

 in many experiments, it was assumed that the averages of the results 

 obtained would represent the digestibility of the nutrients in the present 

 experiments. According to these results, 97 per cent, of the protein and 

 95 per cent, of the fat of cream, and 98 per cent, of the carbohydrates of 

 cream and sugar would be digested;! or, in other words, that 3 per cent, 

 of the protein, 5 per cent, of the fat, and 2 per cent, of the carbohydrates 

 would not be digested and should be found in the feces. By use of these 

 factors it is possible to calculate how much of the total feces should be 

 credited to the cream and sugar and how much to the breakfast food 

 experimented with. Having this data, it is an easy matter to figure the 

 percentage digestibility of each of the nutrients of the cereal alone. 

 Reference to the table showing this data reveals the fact that no figures 

 are given for the digestibility of the fat in the breakfast food alone. This 

 is because the amount of fat in the cereal is so small compared with that 

 in the cream that it was thought that any figures obtained would not be 

 reliable. 



The data required to compute the available energy of the cereal alone 

 consists of the total fuel value of the cereal, the fuel value of the feces 

 for cereal alone, and the fuel value of the organic matter lost in the urine 

 from the incomplete oxidation of the protein of the cereal. By adding the 

 figures for the last two points together and subtracting the sum from the 

 fuel value of the cereal alone, we have the fuel value, or the available 

 energy, of the cereal alone, and by dividing this by the total fuel value of 

 the cereal and multiplying by 100, we obtain the per cent, of the energy 

 of the cereal available to the body. A full statement of the results of the 

 46 successfully completed experiments, figured out as above described, 

 furnished a mass of data which it has been found more convenient to place 

 in the appendix. The average results for each food, however, are given 

 in Table No. 6. 



JStorrs Experiment Station Report, 1899, p. 86. 



