FOOD AS A SOURCE OF ENERGY 33 



of haemoglobin, over 2,000 atoms of oxygen are 

 wanted, of which only 179 are present in the compound. 

 Similarly, in the case of grape sugar, represented 

 by the formula C 6 H, 2 O B , twelve additional oxygen 

 atoms are required for the complete oxidation of the 

 carbon and hydrogen, and for glycerine, C 3 H 8 O 3 , 

 seven more oxygen atoms are requisite. 



Now let us imagine a crowd of persons unwillingly 

 associated and restrained from joining hands with 

 their own particular friends hovering round the 

 outskirts of the crowd. Let us suppose that this 

 restraint is suddenly removed, and that permission 

 be given to friends and relations in the crowd to 

 fraternise with friends and relations outside. The 

 crowd will speedily break up into new associations, 

 smaller groupings, and, if the affinity of individuals 

 be great, considerable friction and heat may be 

 generated in the process of regrouping. This analogy 

 may be crude, but an effort of the imagination will 

 enable us to conceive of an organic compound as 

 such a crowd of units, and the oxygen particles in 

 the atmosphere as their natural affinities outside. 

 Let us make the conditions favourable for the satis- 

 faction of these affinities and at once new combinations 

 are effected, new groupings are established, heat 

 being generated in the process of rearrangement. 

 In the act of combining of the atoms of oxygen with 

 those of carbon, of hydrogen, of sulphur and so on, 

 energy is liberated kinetic energy and the position 

 of separation of these elements from oxygen is 

 therefore a position in which energy is potential 

 ready to be turned into kinetic energy when the 

 combination is permitted. 



Every organism, while alive, is constantly taking Respira- 

 in oxygen in the process known as respiration, tion - 



