60 APPLIED PHYSIOLOGY 



2. Chemical Regulation. 



In addition to the method of varying its heat loss, the 

 temperature of the body can be regulated by increasing 

 or lessening the amount of heat produced. As this 

 method, however, implies the production of variations 

 in the amount of metabolism, it is not used except in 

 emergencies, and for all ordinary contingencies variation 

 of loss is what is relied upon. 



Metabolism in man is at its lowest point when the 

 surrounding temperature is somewhere between 60 and 

 68 F. If it falls below this, metabolism is quickened. 

 and_more heat produced to meet the demand. If, on 

 the other hand, the temperature rises above this, it is 

 difficult indeed, almost impossible, except by curtailing 

 bodily activity for the body to produce less heat, as it 

 is already producing as little as is compatible with the 

 full exercise of the vital powers, and it is accordingly 

 forced to keep its temperature down by increasing the 

 amount of heat lost. 



Muscle is the tissue which is chiefly called upon when 

 greater heat production is demanded. Even in a state 

 of repose, 75 per cent, of the total heat production of the 

 body is derived from the muscles, and when the body is 

 in a condition of activity their share in the production 

 rises to 90 per cent. In normal conditions, therefore, 

 the effect of muscular exercise in raising the temperature 



child's] winter clothing be too warm. ... I would also advise his 

 feet to be washed every day in cold water, and to have his shoes so 

 thin that they might leak and let in water whenever he comes near 

 it ' (' Thoughts concerning Education,' 1690, p. 404). 



