182 PHYSIOLOGY AND HEALTH. 



supply. Consequently^whatever impedes the flow of air into 

 the lungs, and its access to the blood, must so far prevent 

 the development of internal heat, as certainly as any inter- 

 ruption of the draught or diminution of air would lessen the 

 fire and the heat of the fireplace. 



425. Whatever, then, restricts the expansion of the chest, 

 or limits the capacity of the lungs for the admission of air, 

 any pressure of clothing without that prevents the motions 

 of the ribs or the diaphragm, or any disease of the lungs that 

 closes the air-cells within, any of these obstructions, by 

 lessening the amount of oxygen that the blood receives, 

 diminishes the combustion of the atoms of dead flesh and 

 the evolution of the internal heat, as certainly as shutting 

 the draught of a stove would lower or extinguish its fire. For 

 this reason, asthmatic persons, and those whose air-cells are 

 partially closed with disease, are only partially warmed, and 

 cannot endure so severe a cold as men in health. A poor 

 woman, whom I saw sick with consumption in a very cold 

 room, was frozen to death, one night, in her bed, in the 

 winter of 1830, while some other women, who slept in the 

 same room, and under the same quantity of clothing, awoke 

 in vigor, though suffering with cold. 



426. Nothing but oxygen can support this internal com- 

 bustion of fuel. We must not only receive a sufficiency of 

 air into the lungs, but that air must contain its due propor- 

 tion of this gas. If, then, the air contains less than the due 

 quantity,' if it has been breathed over, and its oxygen has 

 been consumed, or if, in" consequence of mixture with other 

 gases, the twenty inches which we inhale conta n less than 

 twenty per cent. of*>xygen, then the internal combustion is 

 impeded, heat is sparingly evolved, and those who breathe 

 this impure or weakened air are comparatively cool. After 

 a crowd has been long in session in a close hall, or children 

 in an unventilated school-room, in winter, they begin to 

 complain of being cold. Notwithstanding the fire may glow 

 in the stove, and the thermometer indicate no reduction of 

 temperature, still, for want of oxygen in the vitiated air, the 



