QUALITY 



lOl 



It will be noted that nothing is said in these diets as to the quan- 

 tity of the food digested and absorbed into the body, as it is from 

 this alone that tissue-formation and heat-energy production can 

 take place — or, in other words, we require to know something as 

 to the quality as well as the quantity of the food supplied in 

 a diet. 



QUALITY. 



In this section we desire to know the amount of any given food 

 which is absorbed, and is therefore available for use in producing 

 heat, energy, and repair. 



The amount which is capable of being digested may be deten:nined 

 by artificial digestion of a sample, but though said to give good 

 results, it is hardly reliable as to absorption. 



A better method is to begin by giving the person to be experi- 

 mented upon a dose of charcoal, and after a few hours to administer 

 a given quantity of the food to be tested of which the protein, 

 carbohydrate, and fat factors are known. The faeces are in due 

 course carefully collected and weighed, and the total amount of 

 nitrogen and of fat determined. From the nitrogen, after deducting 

 0-5 gramme to allow for the daily amount of excreted metabolized 

 nitrogen, can be calculated the amount of protein in the faeces, and 

 this deducted from the amount of protein in the food gives the quan- 

 tity absorbed. 



The fat is determined in the same way by ether extraction, while 

 the carbohydrate is obtained by calculation. 



Nature of Food. 



Protein. 



Carbohydrate. 



Fat. 



Mixed diet : 









Total foods 



92 



97 



95 



Animal foods 



97 



98 



95 



Vegetal foods 



84 



,97 



90 



Meat and fish 



97 



98 



95 



Eggs 



97 



98 



95 



Milk, cheese, etc. 



97 



98 



95 . 



Cereals 



85 



98 



90 



Starches and sugars . . 





98 





Legumes (dried) 



78 



97 



90 



Vegetables 



83 



95 



90 



Fruits . . 



85 



90 



90 



Langworthy gives the table above showing the coefficients of 

 digestibility or the amounts per cent, of the foods which were 

 digested, it must be remembered that by the word ' digestibility ' 

 as used in dietetics is meant not * apparent digestibility,' or the time 

 a food requires to pass through the stomach, but ' actual digesti- 



