NECESSITY FOR CHANGES OF DIET. 255 



So that | Ib. of meat, and less than 2 Ibs. of bread, 

 would supply all the needful carbon and nitrogen with but 

 little waste. 



From these facts it will be plain that a mixed diet is the 

 best and most economical food for man ; and the result of 

 experience entirely coincides with what might have been 

 anticipated on theoretical grounds only. 



It must not be forgotten, however, that the value of 

 certain foods may depend quite as much on their digesti- 

 bility, as on the relative quantities of the necessary 

 elements which they contain. 



In actual practice, moreover, the quantity and kind of 

 food to be taken with most economy and advantage cannot 

 be settled for each individual, only by considerations of the 

 exact quantities of certain elements that are required. 

 Much will] of necessity depend on the habits and digestive 

 powers of the individual, on the state of his excretory 

 organs, and on many other circumstances. Food which to 

 one person is appropriate enough, may be quite unfit for 

 another ; and the changes of diet so instinctively prac- 

 tised by all to whom they are possible, have much more 

 reliable grounds of justification than any which could be 

 framed on theoretical considerations only. 



In many of the experiments on the digestibility of 

 various articles of food, disgust at the sameness of the 

 d'iet may have had as much to do with inability to consume 

 and digest it, as the want of nutritious properties in the 

 substances which were experimented on. And that disease 

 may occur from the want of particular food, is well shown 

 by the occurrence of scurvy when fresh vegetables are 

 deficient, and its rapid cure when they are again eaten : 

 and the disease which is here so remarkably evident in its 

 symptoms, causes, and cure, is matched by numberless 

 other ailments, the causes of which, however, although 

 analogous, are less exactly known, and therefore less 

 easily combated. 



