METABOLISM, NUTRITION, AND DIET 



From the data on page 342, it is possible to form various diet-scales 

 which shall supply the needs of different conditions of growth and decay 

 of the body. In an economical daily ration consisting of meat, bread, 

 butter, cheese, potatoes and vegetables one might supply the requisite 

 amount of protein nitrogen as follows: 



N. Proteins. 



340 grams lean uncooked meat 10.0 grams 62.5 grams 



600 grams bread 6.0 grams 37.5 grams 



90 grams butter 0.5 grams 3.1 grams 



28 grams cheese 1.5 grams 9.4 grams 



225 grams potatoes \ i . o grams 6.2 grams 



225 grams carrots. / 



19.0 grams 118.7 grams 



The 30 grams of salts necessary to replenish the daily loss by excretion 

 in the urine are contained in the meat 16 grams, the bread 12 grams, and 

 vegetables about 4 grams. 



The fluid should consist of about 2,500 to 2,800 grams, and might be 

 given as water, with or without tea, coffee, or cacao, which are chiefly 

 stimulants. 



The Energy Requirements of the Body. The food must not only 

 make up for the substances eliminated from the body but must also supply 

 the potential energy of heat and motion set free in the living body. The 

 amount of heat is measured in terms of calories, or more often in large 

 Calories. The work energy may be expressed in gram-centimeters, or in 

 kilogrammeters. Since one calorie of heat is the equivalent of 42,670 gram- 

 centimeters of work, the two units may be computed interchangeably. 



The source of the heat and work energy which is produced in the body is 

 from the metabolic changes of the tissues, the chief part of which is in the 

 nature of oxidation, since it may be supposed that the oxygen of the atmos- 

 phere taken into the system is ultimately combined with carbon and hydro- 

 gen. Any change, indeed, which occurs in the protoplasm of the tissues, 

 resulting in an exhibition of protoplasmic function, is attended by the evolu- 

 tion of heat and the formation of carbon dioxide and water. The more act- 

 ive the changes the greater is the amount of heat produced. In order that 

 the protoplasm may perform its functions, the waste of its own destructive 

 metabolism must be repaired by the due supply of food material to be built 

 up in some way into the protoplasmic molecule. In the tissues, as we have 

 several times remarked, two processes are continually going on: the building 

 up of the protoplasm from the food, anabolism, which is not accompanied 

 by the evolution of heat; and the oxidation of the protoplasmic materials, 

 katabolism, resulting in the production of energy, by which heat is set free. 

 Food is therefore necessary for the production of heat. It is not neccessary 

 to assume that the combustion processes, indeed, are as simple as the bare 

 statement of the fact might seem to indicate. But complicated as the vari- 



