ANIMAL HEAT. 187 



temperature at 102. Full-grown magpies lost 5 of heat in 

 the same atmosphere, and in the same time that young birds 

 of the same species lost 25 of heat. The same law applies 

 to children and men. Infants and old men cannot, therefore, 

 endure the cold so well as men of middle life, and need more 

 careful protection of clothing when exposed. 



436. " The state of natural sleep is in general accompa- 

 nied by a diminution of the power of producing heat." The 

 body is then more susceptible of the influence of cold. Thus 

 the consumptive woman ( 425, p. 182) was frozen during 

 her sleep. Night travellers are in much more danger of 

 suffering from the cold if they allow themselves to sleep 

 than if they keep awake. 



437. The amount of heat given out from the combustion 

 of a definite quantity of carbon or hydrogen, or the union 

 of either of these with oxygen, has been determined by 

 experiments. It is found, also, to be the same wherever this 

 combustion takes place, whether in or out of the living body, 

 and whether it happens rapidly and with a flame, as in the fire 

 of a furnace, or slowly, atom by atom, as in the textures of 

 the animal body. If, then, we can ascertain the amount 

 of these elements which are consumed in the living system, 

 and in any given time, we can determine the amount of heat 

 which will be then evolved. 



438. In the course of twenty-four hours, there are, on 

 an average, 13.9 ounces of carbon converted into carbonic 

 acid gas, and given out from the lungs of every adult in 

 good health. Every ounce of carbon, during the process of 

 combustion, evolves as much heat as would raise 78.15 

 ounces, or almost five pounds, of water, at 32, or the tem- 

 perature of ice, to 212, or the boiling point ; and, conse- 

 quently, the 13.9 ounces of carbon, which are consumed 

 in the human body daily, must give out heat enough to raise 

 67.9 pounds of water from 32 to boiling heat. So much 

 heat from this cause is, then, generated in the body of a 

 person of the average size and in good health, in each day.* 



* Liebig's Animal Chemistry, Part I. V. 



