244 THE PHYSIOLOGY OF MUSCULAK WORK 



small number upon that of the rectum. It is easy to appreciate 

 the reasons of delicacy which prevent the determination of the 

 temperature in the rectum in the case of most patients, but there 

 is no excuse for the constant neglect on the part of clinicians to 

 mention in their reports the time and place where the temperature 

 was taken. Accurate results can only be obtained by the deter- 

 mination of the temperature in the rectum or stream of urine, 

 for the cavity of the mouth is bounded by such thin walls, and 

 is so readily cooled by exposure, breathing, and sweating, that 

 it often does not indicate the true internal temperature of 

 the body. 



The temperature of man shows a daily variation ; it rises 

 during the day, the time of activity, and falls during the night, 

 the time of rest and sleep. The range is from 36'0 (96'8) to 

 37'8 (100'0) ; these are average figures for the temperature of 

 the rectum and urine, and do not include the absolute physio- 

 logical range. 



The temperature is raised during muscular work (*&) ; it may 

 be as high as 38' 9 (102) in a healthy man. This truth is now 

 generally accepted, although a few years ago, owing to observa- 

 tions based upon temperatures taken in the mouth, it was generally 

 denied or contested. The explanation of the disagreement is found 

 in the fact that the temperature of the mouth may fall during the 

 time that the temperature in the rectum and urine is raised. 



The heat of the body depends upon the production and loss of 

 heat. During muscular work the production is greatly increased, 

 owing to the vigorous combustion of material in the tissues, espe- 

 cially in the active muscles. This combustion is indicated by 

 the great rise in the discharge of carbon dioxide and in the ab- 

 sorption of oxygen. The loss of heat also undergoes an augmenta- 

 tion, otherwise the temperature of the body would steadily rise, 

 and would soon reach a height incompatible with the performance 

 of work and even with life itself. Indeed this does occur under 

 special conditions, when a man is forced to work in a hot atmos- 

 phere so laden with moisture that the cooling of his body by the 

 evaporation of sweat is prevented. 



Under ordinary conditions the effect of muscular work is to 

 cause a rise in the internal temperature ; the increased production 

 of heat is not compensated by a corresponding loss. It appears 

 that a rise of temperature, within certain narrow limits, is bene- 



