IMPORTANCE OF HYDROGEN. 23 



furnishing the necessary resistance to the action of the 

 atmospheric oxygen. 



In our climate, hepatic diseases, or those arising from 

 excess of carbon, prevail in summer ; in winter, pul- 

 monic diseases, or those arising from excess of oxygen, 

 are more frequent. 



The cooling of the body, by whatever cause it may 

 be produced, increases the amount of food necessary. 

 The mere exposure to the open air, in a carriage or on 

 the deck of a ship, by increasing radiation and vaporiza- 

 tion, increases the loss of heat, and compels us to eat 

 more than usual. The same is true of those who are 

 accustomed to drink large quantities of cold water, 

 which is given off at the temperature of the body, 98'5. 

 It increases the appetite, and persons of weak constitu- 

 tion find it necessary, by continued exercise, to supply 

 to the system the oxygen required to restore the heat 

 abstracted by the cold water. Loud and long continued 

 speaking, the crying of infants, moist air, all exert a 

 decided and appreciable influence on the amount of food 

 which is taken. 



IV. In the foregoing pages, it has been assumed, that 

 it is especially carbon and hydrogen, which, by com- 

 bining with oxygen, serve to produce animal heat. In 

 fact, observation proves that the hydrogen of the food 

 plays a not less important part than the carbon. 



The whole process of respiration appears most clear- 

 ly developed, when we consider the state of a man, or 

 other animal, totally deprived of food. 



