234 APPLIED PHYSIOLOGY 



408. Sensation of heat and cold. If the temperature is 

 lowered only a degree, there is a feeling of coldness called 

 a chill. A chill is a recognized sign of beginning illness. 

 The ordinary feeling of heat or cold is due to the state of 

 the nerves of the skin, whose special duty is to conduct 

 sensations of temperature. These nerves are so abundant 

 in the skin that their sensations overpower the sensations 

 of the rest of the nerves of the body. If the skin is warm, 

 the whole body feels warm ; while if the skin is cold, the 

 whole body feels cold. 



409. Chills during a fever. It often happens during a fever 

 ehat the blood goes to deeper parts, leaving the skin pale and without 

 its usual supply of heat, and so the whole body feels cold, and the per- 

 son has a chill, although the temperature of the body may be raised 

 several degrees. 



In severe sickness the heart is sometimes too weak to pump the 

 blood to the skin, and so it feels cold, although the temperature of the 

 inside of the body may be raised several degrees. This condition is 

 often called inward fever. On the other hand, the body may be cold, 

 and yet if the blood is brought to the surface, the person will feel warm. 



410. Regulation of the heat produced. The amount of 

 heat produced in the same body varies widely at different 

 times, and some persons always produce many times as 

 much as do others. So in order to keep the temperature 

 constant, heat must be given off at one time and saved at 

 another. Nature regulates the temperature of the body 

 by varying both the amount produced and the amount 

 given off. The production of heat depends partly upon 

 the amount of food. In summer man naturally eats less 

 than in winter. Inhabitants of arctic regions eat large 

 quantities of fat, the oxidation of which produces a large 

 amount of heat, while the inhabitants of hot climates 

 naturally avoid fat. 



