THE TEMPERATURE OF THE BODY 1309 



With these diurnal changes in temperature are associated parallel 

 oscillations in the rate of metabolism as shown by the elimination of 

 carbon dioxide. They are probably determined by the changes in the 

 movement and tension of the muscles occurring during the waking 

 hours. If the habits of a man or animal be reversed, so that he 

 sleeps in the daytime and performs his normal vocation by night, it 

 is possible to reverse also the direction of the diurnal variations in 

 temperature. The temperature may be also affected temporarily 

 by various acts, such as taking of food, or the muscular work ; the 

 influence of the latter factor is often very marked. In many individuals 

 a hard game at tennis suffices to raise the temperature to 39 C. 

 (100 F.), and even the healthiest individual will show some change in 

 his temperature as the result of exercise. Pembrey found that the 

 act of marching, especially in the ill-adapted clothes of the British 

 soldier, led to a considerable rise in temperature, a rise which is 

 apparently responsible for the discomfort and fatigue observed under 

 such circumstances. Such a change in the body temperature is merely 

 temporary in its effects, and insignificant in comparison with the 

 wonderful uniformity of temperature observed in men of all races and 

 of all climes under most varying conditions of food and activity. 



Just as there are limits to the power of the organism to regulate 

 its temperature when there is an excessive formation of heat in the body, 

 so there are limits to the regulation of temperature to severe altera- 

 tions in the temperature of the external medium. Thus if the body is 

 subjected to excessive external cold, or the loss of heat be increased 

 by absence of clothes, by depriving an animal of its fur, or by immer- 

 sion in a cold bath, the temperature of the body may sink continuously. 

 This fall of temperature in the higher animals is very soon followed by 

 paralysis of the highest nerve-centres and loss of consciousness. The 

 centres in the medulla are later on affected, so that the respiration is 

 slowed and the blood pressure falls. If the temperature does not 

 fall too low it is possible to revive the animal or man by checking the 

 loss of heat or by supplying artificial warmth. Recovery has in fact 

 been observed in men in whom, as a result of exposure, the body 

 temperature had fallen to 24 C. In the same way exposure to extreme 

 heat, especially associated with muscular exercise and increased 

 production of heat in the body, may cause a rise of the body tempera- 

 ture. A man, or animal, whose temperature is raised above the normal, 

 is said to be in a state of pyrexia. A rise of 2 or 3 C. is associated 

 with all the phenomena which characterise fever, i.e. quickening of 

 pulse and respiration, malaise, headache, and loss of muscular power. 

 If j the temperature rise to a greater degree than this the patient 

 may lose consciousness, and death ensues at a temperature of about 

 44 C. 



