SOURCES OF ENERGY IN THE BODY. 291 



Body are highly or completely oxidized, tolerably simple 

 chemical compounds; and its material income is mainly 

 uncombined oxygen and oxidizable substances, the former 

 obtained through the lungs, the latter through the alimen- 

 tary canal. In energy, its income is the potential energy 

 of uncombined or feebly combined elements, which are 

 capable of combining or of forming more stable compound^ 

 and its final expenditure is kinetic energy almost entirely 

 in the form of mechanical work and heat. Given oxygen, 

 all oxidizable bodies will not serve to keep the Body alive 

 and working, but only those which (1) are capable of ab- 

 sorption from the alimentary canal and (2) those which are 

 oxidizable at the temperature of the Body under the influ- 

 ence of protoplasm. Just as carbon and oxygen will not 

 unite in the furnace of an engine unless the "fire be 

 lighted" by the application of a match but, when once 

 started, the heat evolved at one point will serve to carry on 

 the conditions of combination through the rest of the mass, 

 so the oxidations of the Body only occur under special con- 

 ditions; and these are transmitted from parent to offspring. 

 Every new Human Being starts as a portion of protoplasm 

 separated from a parent and affording the conditions for 

 those chemical combinations which supply to living matter 

 its working power : this serves, like the energy of the 

 burning part of a fire, to start similar processes in other 

 portions of matter. At present we know nothing in physi- 

 ology answering to the match which lights a furnace; those 

 manifestations of energy which we call life are handed 

 down from generation to generation, as the sacred fire in 

 the temple of Vesta from one watcher to another. Science 

 may at some time teach us how to bring the chemical con- 

 stituents of protoplasm into that combination in which 

 they possess the faculty of starting oxidations under 

 those conditions which characterize life; then we will have 

 learnt how to strike the vital match. For the present 

 we must be content to study the properties of that form 

 of matter which possesses living faculties; since there is no 

 satisfactory proof that it has ever been produced, within 



