WHY DO WE EAT OUR DINNER? 807 



these have lost or given up all their energy, they are naturally of no 

 more use to the body than the similar carbonic acid and steam which 

 fly up the draught are of use to the engine. Accordingly, they are taken 

 up by the stream of blood as it passes, separated from the useful com- 

 ponents of that compound liquid by an appropriate organ, and rejected 

 from the body as of no further service. 



But their place in the muscle must once more be supplied by fresh 

 energetic materials ; and these materials are brought to it by the self- 

 same blood vrhich removes the deenergized waste products. And now 

 we begin to see why we must eat our dinners or starve. Every time 

 our heart beats, every time our lungs draw in a breath, a certain amount 

 of matter in the tissues of the muscles which produced those motions un- 

 derofoes oxidation, and is carried off in the oxidized form to be cast out 

 of the body as waste. Every new pulsation or breath requires a certain 

 new quantity of energetic material, both as food-stuffs and as oxygen ; 

 and hence we must supply the one from the stomach and the other from 

 the lungs if we wish to keep the mechanism going. The store of hydro- 

 carbonaceous matters laid by in the body is generally considerable in 

 well-fed persons ; for, besides the contents of the muscles themselves, 

 we have usually a large reserve fund in the shape of fat, ready to be 

 utilized when occasion arises. Hence, we can get along for a very 

 short time, if necessary, without food ; because we can fall back, first 

 upon the fat-reserve, and then upon the muscles and tissues, for ener- 

 getic materials. But after a time the ceaseless beating of the heart and 

 movement of the lungs will use up all the available matters, and the 

 blood will cast off the oxidized product and excrete it from the body ; 

 till at last no more materials are forthcoming, the whole contents of the 

 tissues have been oxidized and got rid of, and the heart and lungs must 

 perforce cease to act, in which case the unhappy victim is said to have 

 died of starvation. As regards the supply of oxygen, on the other 

 hand, we are very much more restricted in our power of endurance ; 

 for we have no large store of this necessary for combustion laid by in 

 our bodies, and if the supply be cut off for a single moment (as by com- 

 pressing the throat or suffocating with carbonic acid) the heart and 

 lungs must cease at once to act, and death takes place immediately. 

 For of course death, viewed on its purely physical side, means the ces- 

 sation of that set of activities w^iich results from the union of oxygen 

 with the food-stuffs in the body. 



By this time I hope the reader can see quite clearly what is the 

 necessity for eating his dinner. If we are to live, we must keep up 

 the cycle of our bodily activities, and especially those two fundamental 

 ones, the breathing of the lungs and the beating of the heart. In order 

 to do this, we must supply the muscles employed with the two energy- 

 yielding substances, oxygen and hydrocarbons. The supply of oxygen 

 must be continuous ; in other words, we must never for a moment 

 leave off breathing ; but the supply of hydrocarbons may be intermit- 



