AND ANIMAL HEAT* 193 



coldness of the extremities ensues. If, on the other 

 hand, the mind and nervous system be stimulated 

 by cheerful exertion and agreeable emotions, a 

 pleasant glow pervades the frame, and external cold 

 is much more easily resisted. 



The quantity and quality of the food and state of 

 the digestive functions are also important conditions. 

 This will be readily assented to, when the reader 

 considers that a due supply of well-formed chyle is 

 required to restore the nourishing properties of the 

 blood, and that if, in consequence either of insuf- 

 ficient food or of weak digestion, this be rendered 

 impossible, all the animal functions, among others 

 the production of heat, must necessarily be impaired. 

 This is the reason why cold is felt most severely in 

 the morning before breakfast, and why coldness of 

 the feet and chilliness of the surface are so gene- 

 rally complained of in indigestion and bilious com- 

 plaints. 



Everybody knows that exercise favours, and in- 

 dolence obstructs, the development of animal heat. 

 Exercise produces its effect by the general stimulus 

 which it gives directly to the respiratory and circu- 

 lating systems, and indirectly to the nervous and di- 

 gestive functions. 



In attempting, therefore, to increase the power 

 of resistance to cold in the human body, we ought 

 to take into account all the conditions which favour 

 the generation of heat. Observation proves that 

 the degree of cold required to overcome the internal 

 generating power, and to extinguish life, varies in 

 the same individual at different times ; and there- 

 fore our protecting measures also ought to be varied 

 according to the state of the constitution, the vig- 

 our of the respiratory and digestive functions, the 

 kind of food, and the amount of exercise. When 

 the food is inadequate, and the mind depressed, the 

 system resists the impression of cold with great dif- 

 ficulty ; and even in Scotland, where the tempera- 

 R 



