Chap. XVIII] BODY HEAT 357 



and a loss of temperature result ; or shivering may intervene. In 

 this case the muscular contractions and constriction of the blood- 

 vessels stimulates metabolism and heat production. Wnen cold 

 baths are given for the purpose of increasing heat elimination, 

 friction is used during the bath to prevent shivering. Friction 

 stimulates the sensory nerves of the skin, causes dilatation of the 

 arterioles, and favors the flow of hot blood to the surface, thus 

 decreasing the sensation of cold and increasing heat elimination. 

 If properly given, cold baths stimulate the nervous system, improve 

 the tone of the muscles, including the muscles of the heart and 

 blood-vessels, stimulate the circulation, and favor the elimination 

 of heat. 



VARIATIONS IN TEMPERATURE 



Normal variations. — The temperature of the human body is 

 usually measured by a thermometer placed in the mouth, axilla, 

 or rectum. Such measurements show slight variations, as the 

 temperature in the interior of the body is slightly higher than on 

 the surface of the skin. The average temperature in the rectum ^ 

 is 98.9° F., in the axilla is 98.4° F., in the mouth is 98.3° F. 



Other normal variations depend upon the manner of living, 

 time of eating, age, etc. The lowest temperature is usually in the 

 early morning, it rises slowly during the day, reaches its maximum 

 in the evening, and falls again during the night. This corresponds 

 to the usual temperature ranges in fever, when the maximum is in 

 the evening and the minimum in the early morning. Muscular 

 activity and food may also cause slight increase in temperature 

 during the day. Age has some influence. Infants and young 

 children have a slightly higher temperature than adults. It is 

 also true that the heat-regulating mechanism in infants^ and young 

 children is not so efficient as in adults, consequently they are more 

 subject to changes of body temperature, and these changes are not 

 as significant as they would be with adults. Aged people show a 

 tendency to revert to infantile conditions, and their temperature 

 is usually slightly higher than in middle life. 



1 Rectal temperature is the most reliable, and that by mouth (if properly taken) 

 is almost equally reliable. Axillary temperature has little value. 



* At birth the heat-regulating mechanism is not "in working order," and during 

 the first few weeks of life infants are not able to regulate their body temperature, 

 hence the importance of keeping them warm. Premature infants are even less able 

 to regulate their body temperature, hence need of special means to keep them 

 warm. 



