HEAT IN RELATION TO THE HUMAN BODY 27 



sugars, and fats that are body fuels. On the other hand, one- 

 seventh or more of the food needed by the body is required 

 for rebuilding the various tissues. Foods that serve this spe- 

 cial purpose are known as proteins. Starch, sugars, and fats 

 are classed as carbohydrates. The energy from oxidation in 

 the body maintains a temperature necessary for the various 

 organs to perform their several functions (duties) . The chem- 

 ical products of this oxidation in the body, even as in the 

 combustion of coal or oil, are largely carbon dioxide and 

 water. 



Most of the processes within the body are normally carried 

 on without conscious effort. If it were necessary to give 

 attention to every act in respiration, or to attend to what is 

 now the involuntary action of the heart muscles, little else 

 could be done. One might forget to breathe, or to keep 

 the heart beating regularly. Freed from the necessity of 

 directing the bodily mechanism, the mind can be employed in 

 directing the expenditure of the excess energy of the body in 

 those physical and mental efforts involved in earning a 

 livelihood or in promoting culture, health, and happiness. 



The living matter contained in the cells of the different 

 body tissues cannot endure any considerable change in tem- 

 perature without harm to it and possible destruction of its 

 life. One of the functions of the skin through secretion of 

 perspiration is to regulate the body temperature so that in 

 health it varies but little summer or winter, regardless of 

 whether one is indoors or out. As the perspiration evaporates 

 from the surface of the body heat is required to vaporize the 

 water. This heat is provided in part from the body, and 

 the more profuse the perspiration and the more complete 

 its vaporization, the larger is the amount of heat taken from 

 the body. The higher the body temperature as result of 

 jnuscular exercise the more active is the secretion of perspi- 

 ration by the glands in the skin. It is nature's provision that 



