REQUISITES OF A NORMAL DIET 449 



taking a very small quantity of food, or even by water alone. The cases 

 so frequently related of survival after many days or even some weeks of 

 abstinence have been due either to the last- mentioned circumstances, or to 

 other no less effectual conditions which prevented the loss of heat and 

 moisture. 



During the starvation period the excretions diminish. The urea, as rep- 

 resenting the nitrogen, falls quickly in amount, reaches a minimum where it 

 remains constant for several days, then finally falls rapidly immediately 

 before death. The sulphates and phosphates undergo much the same type 

 of reduction. The carbon dioxide given out and the oxygen taken in di- 

 minish. The feces diminish as well as the bile. It is highly probable 

 that the greater part of the nitrogen represents the loss of weight of the 

 muscles. 



In starvation, then, we see that the only income consists of water and 

 the inspired oxygen. The whole of the energy of the body given out in the 

 form of heat and mechanical labor is obtained at the expense of its own 

 tissues, there being as a result a constant drain of the nitrogen and carbon, 

 not to mention the other elements of which the tissues are composed. It is 

 obvious that such a condition cannot be endured for any length of time. 



REQUISITES OF A NORMAL DIET. 



It will be understood from the preceding discussion that it is necessary 

 that a normal diet should be made up of the various classes of foods in suffi- 

 cient quantity to supply the same amounts of carbon and nitrogen that are 

 gotten rid of by the excreta. No doubt these desiderata may be satisfied 

 by many combinations of foods, and it would be unreasonable to expect the 

 diet of every adult to be the same. The age, sex, strength, and circum- 

 stances surrounding each individual must ultimately determine what he 

 takes as food. A dinner of bread and cheese with an onion contains all the 

 requisites for a meal, but such diet would be suitable only for those possessing 

 strong digestive powers. It is a well-known fact that the diet of the con- 

 tinental nations differs from that of our own country, and that of cold from 

 that of hot climates, but the same principle underlies all, viz., the replace- 

 ment of the losses of the body in the most convenient and economical way 

 possible. Any one in active work requires more food than one at rest, and 

 growing children require more food in proportion to body weight than adult 

 men and women, but of a different variety. 



The chief diet-scales which have been drawn up with the object of 

 supplying the proximate principles in the required proportions are given in 

 the table below: 



29 



