950 



NUTRITION AND HEAT REGULATION. 



to (p. 911), makes it increasingly probable that the different 

 proteins or even the different carbohydrates or fats may be found 

 to have each a specific influence upon metabolism. And, lastly, 

 specific substances may be found in the foods (food accessories or 

 vitamines), which in some as yet undetermined way are important 

 or essential to the metabolism of some part of the body. In these 

 respects the science of dietetics has a wide field for investigation. In 

 a general way, however, the heat energy of a food expresses its value 

 as a means for supplying the energy needs of the living cells. In the 

 work that these cells perform, whether it is contraction, secretion, 

 or nervous activity, energy is needed, and this energy is carried 

 into the body in the potential chemical energy of the proteins, fats, 

 and carbohydrates, whatever may be the source from which these 

 foodstuffs are obtained. 



Dietetics. The subject of the proper nourishment of individ- 

 uals or collection of individuals in health and in sickness is treated 

 usually in works upon hygiene or dietetics. The practical details 

 of the preparation and composition of diets must be obtained 

 from such sources.* The general principles upon which practical 

 dieting depends have been obtained, however, from experimental 

 work upon the nutrition of man and the lower animals, some 

 account of which has been given in the foregoing pages. In a 



* For practical directions, see Gautier, "I/ alimentation et les regimes," 

 1904; Blyth, "Foods: their Composition and Analysis "; Rose, "Feeding the 

 Family," New York, 1916. 



