91 
THE BREATH OF LIFE. 
BY W. CKOOKES, F.C.S. 
N OT only figuratively, but in actual reality, can tlie life of 
man be compared to a fire, or lighted candle. Respira- 
tion may be regarded as the same process as combustion, only 
performed in a slower manner. Fuel is placed in a furnace, and 
the combustion which we see take place with the evolution of 
heat and light is owing to the combination of the oxygen — that 
wonderful constituent of the atmosphere — with the carbon and 
hydrogen of the fuel. In a similar way we place food (which is 
fuel) in our bodies, and then by tbe act of respiration we draw 
into the lungs oxygen, and this, uniting with the carbon and 
hydrogen of the food, also produces a disengagement of heat. 
Another point worthy of attention is, that the combustible 
matter of the food — the carbon and hydrogen — when burned in 
the body by means of air drawn in by the lungs, produces 
exactly the same amount of heat as it would have done had the 
same quantity been consumed in an ordinary furnace by means 
of the free atmospheric oxygen ; the only difference being, that 
in the latter case the combustion takes place rapidly, evolving 
an intense heat for a short time, whilst in our bodies the fuel is 
burned more slowly, thus evolving less heat for a longer time, 
the total amount of heat liberated by the combustion of a given 
weight of carbon, whether it be burned in the form of coal or 
beef, being always the same. 
This, therefore, is the cause of the high temperature of the 
human body. We each carry about within us a portable furnace 
of the most perfect construction. Fuel is thrown on at intervals 
during the day, the need of a fresh supply being made known 
by the feeling of hunger (as it is in some steam-engines by the 
ringing of a bell) ; whilst a draught of air is drawn in at each 
inspiration, by which means the process of combustion proceeds 
uninterruptedly. 
The analogy is strictly correct, even if pursued further. 
In a furnace we can augment the energy of combustion by 
increasing the draught of air ; and so in our bodies, if we 
increase the normal number of respirations per minute, a con- 
siderable rise of temperature is the result, the excess of heat 
being radiated into the surrounding atmosphere, and carried off 
