186 PHYSIOLOGY AND HEALTH. 



inflammations, &c., the heart beats quicker, and the flow of 

 blood is more rapid than natural, and there is a greater pro- 

 duction of heat. But in some other diseases, as asthma, 

 cholera, &,c., there is, on the contrary, a greater coldness 

 The internal warmth is affected by the condition of the 

 nervous system, by excitements and depressions, by the 

 emotions, the passions, and the states of mind. One is burn- 

 ing with anger or with love. The exciting and the ardent 

 passions quicken the flow of the blood, and increase the 

 internal heat, while the depressing passions diminish it. 

 Cheerfulness and merriment promote the evolution of heat, 

 while fear, sorrow, and despondency impede it. 



434. Fatigue, exhaustion, hunger, night-watching, sleep- 

 lessness, indigestion, or any thing that depresses the system 

 and diminishes the energies of life, lessens the production of 

 heat, and the power of resisting cold. In this condition, one 

 cannot bear exposure to a low temperature as ^well as when 

 he is fresh and vigorous. He is then more liable to take 

 cold. Visiting a friend, a public officer, in the afternoon of 

 a pleasant day of March, I found him shivering over a fire, 

 though otherwise in good health. He said that he had been 

 out to walk, and was chilled. It was a warm day, and other 

 men complained of the heat; but they were vigorous, for 

 they had been lefreshed by their night's sleep; but he, hav- 

 ing an important report to finish, had sat up, and labored 

 upon it with all his mental energy, until two o'clock in the 

 morning; then, being exhausted, he retired, but awoke in 

 the morning still fatigued and unrefreshed ; consequently, he 

 had not sufficient power to maintain his proper heat, even in 

 a temperature which was comfortably warm to men in the 

 enjoyment of their usual vigor. 



435. In the different periods of life, there is a difference 

 of power of producing internal heat. It is more feeble in 

 infancy and in old age than in the vigorous years of youth 

 and manhood. Dr. Edwards exposed some young and old 

 sparrows to a temperature of 64 with the same amount of 

 protection. At the end of a definite period, the young were 

 cooled down to 60, while the older birds maintained their 



