368 STUDIES IN ADVANCED PHYSIOLOGY. 



in the nitre, together with the other substances, are mixed 

 together in such a way as to hold a large amount of latent 

 energy. Gunpowder possesses enough oxygen within itself 

 to burn itself up completely. In fact, it is this intra-molar 

 oxidation which is the explosion. Gunpowder explodes be- 

 cause in every part of its substance there is enough oxygen 

 present to burn up the other ingredients. 



So we must imagine that the living cell is able in some 

 at present entirely inexplicable way to take dead proteid 

 and salts and to combine these with the oxygen from the 

 lung in such a way that a kind of living gunpowder pos- 

 sessing much latent energy is produced. This view of the 

 use of the oxygen from the lung changes completely the 

 current notion. Usually we speak of the necessity of get- 

 ting more oxygen in exercise in order that there may be a 

 larger supply of this gas to burn up the tissues and so pro- 

 duce the energy. According to this view (and there is 

 every probability that it is the correct one) the extra de- 

 mand of the oxygen in exercise results from the necessity 

 of building up new living tissue, of making new living gun- 

 powder to replace that which has been used up in the exer- 

 cise in question. The oxygen, then, is not the cause of the 

 liberation of the energy; it is the result. Just as in a bat- 

 tle there would be greater demands for fresh supplies of 

 gunpowder to replace the increased amounts being used up. 



This constructive building up of proteids and oxygen 

 into living matter does not present the difficulties which at 

 once appear when we think of the sugars and the fats. The 

 question arises, in what manner do these foods figure? In 

 the first place it is well to remember that according to this 

 view proteids alone can build up new tissue. Sugars and 

 fats by themselves cannot do so. Of course such a thing is 

 a chemical absurdity. We must therefore credit to the pro- 

 teid every bit of new tissue that appears, and imagine its 

 appearance in the manner just indicated. 



The main characteristic of living tissue is its ability 

 to do some kind of work. Life in this sense is energy, 



