180 



PHYSIOLOGY AND HEALTH. 



which it carries along with it, reach the minute arteries and 

 the capillaries, where the work of nutrition is carried on, 

 the interchange of the old for the new particles of flesh takes 

 place. The old those which have finished their work and 

 are dead give way, and the new ones, fresh with living 

 vigor, take their stations and perform their part in the work 

 of life. As these old and dead atoms of flesh pass from their 

 stations to the vessels, the oxygen in the blood meets them, 

 and they unite together and form new compounds. The 

 union of the oxygen with the carbon produces carbonic acid, 

 and its union with hydrogen produces water. These unions 

 take place in the same manner, and the same results follow, 

 as when the carbon of the wood in the fireplace, and the 

 hydrogen of the gas lamp, unite with oxygen. The carbon 

 and the hydrogen are burned, fire is produced, and heat is 

 evolved ; the carbonic acid and the water are then carried 

 through the veins to the heart and the lungs, and the heat is 

 left in the textures of the living body. During this process, 

 precisely the same amount of heat is given out from this in- 

 ternal fire this slow combustion of the wasted particles of 

 flesh as would result from the combustion of the same 

 amount of fuel, carbon, and hydrogen elsewhere. 



CHAPTER IV. 



Exercise increases Combustion of Carbon and Evolution of Heat. 

 Whatever increases Flow of Blood increases Heat, and whatever 

 diminishes Flow of Blood lessens Heat. Oxygen and Fuel neces- 

 sary to support internal Fire. Whatever interrupts Supply of 

 Oxygen or Air to Lungs, prevents Development of Heat. Tight- 

 Lacing lessens Heat. Bad Air foul Air lessen it. Food 

 supplies Fuel. Well-fed warmer than the Ill-fed. Alcohol does 

 not increase the Heat of the Body. Meat supplies more Fue 

 than Bread. More Meat eaten in cold than in warm Weather. 



422. THIS work of interchange of particles, and of burn- 

 ing the old flesh, is carried on throughout the whole body ; 



