I OXIDATION AND HEAT PRODUCTION 25 



leaves the body contains more oxygen tlian the food which 

 enters the body. Indeed oxidation, the oxygen being 

 supplied by the blood, is going on all over the body. 

 All parts of the body are thus continually being oxidised, 

 or, in other words, are continually burning, some mure 

 rapidly and fiercely than others. And this burning, 

 though it is carried on in a peculiar manner, so as never 

 to give rise to a tiame, yet nevertheless produces an 

 amount of heat which is as efficient as a fire to raise the 

 blood to a temperature of about 37' C. (98'6' F.) ; and this 

 hot fluid, incessantlj' renewed in all parts of the economy 

 by the torrent of the circulation, warms the body, as a 

 house is warmed by a hot-water apparatus. Nor is it 

 alone the heat of the body which is provided by this 

 oxidation ; the energy which appears in the muscular 

 work done by the body has the same source. Just as the 

 burning of the coal in a steam-engine supplies the motive 

 power which drives the wheels, so, though in a peculiar 

 way, the oxidation of the muscles (and thus ultimately of 

 the food) supplies the motive power of those muscular 

 contractions which carry out the movements of the body. 

 The food, like coal combustible or capable of oxidation, 

 is built up into the living body, which in like manner 

 combustible, is continually being oxidised by the oxygen 

 from the blood, thus doing work and giving out heat. 

 Some of the food perhajjs may be oxidised without ever 

 actually forming part of the body or after it has already 

 become waste matter, but this does not concern us 

 now. 



11. Coordinating Action of the Nervous System. — 

 These alimentary, circulatory or distril>utive, excretory, 

 and respiratory (oxidational) processes would however be 

 worse than useless if they were not kept in strict propor- 

 tion one to another. If the state of physiological balance 

 is to be maintained, not only must the ijuantity of aliment 

 taken be at least equivalent to the quantity of matter 

 excreted ; but that aliment nmst be distributed with due 



