GENERAL PRINCIPLES 51 



Speaking broadly, we might say that the molecular energy of 

 matter has two alternative destinations. On the one hand, if 

 directed and controlled, it can do useful work. On the othei 

 hand, if left to itself without such direction and control, it inevi- 

 tably tends to be dissipated in heat. 



Helmholtz described these two conditions as those of moleculai 

 order and disorder respectively. An analogy might be found in 

 the case of a body of troops marching. If, acting under orders., 

 their progress will be orderly and regular ; if left to themselves, 

 disorder and confusion will result. 



Disorder more easily than order can occur in molecular move- 

 ments as among troops ; the state of degradation being the more 

 probable one. 



Not less curious is the fact that chemical energy can transform 

 itself into all the other forms, without any one of the latter being 

 able in their turn to transform themselves into chemical energy. 



Nevertheless, solar radiation, or even a source of artificial 

 light acting on the green leaves of plants, has an effect on living 

 matter. The chlorophyll of vegetables is indispensable to that 

 work of synthesis. Chemical energy thus accumulates little by 

 little, in vegetable bodies, from every diminution. 



It must be recognised that solar radiation is the origin of all 

 the energy in the world, whilst the two poles of energetic trans- 

 formation are chemical energy and heat energy. 



38. Vital Energy. The teachings of energetics are just as true 

 in regard to the animate world as the inanimate world. Thus 

 the number of calories given to an organism by a given quantity 

 of food is found to correspond exactly with the calories radiated 

 from that organism. If work is done the number of calories 

 required by the law of equivalence will be absorbed, the rest 

 being equally radiated to the exterior. Therefore vital energy 

 represents nothing quantitatively, and there is no place for it in 

 the cycle of energy (see 103). Does an intellectual energy 

 absorbed by all the manifestations of thought exist ? Appar- 

 ently not, because experiment has shown that the balance of the 

 energies is always exact and always the same whether a man 

 takes up or does not take up intellectual occupations (see 149). 

 Finally, among the elements of cerebral nervous matter, does 

 there exist a source of intellectual energy which may not be 

 perceptible by our methods of measurement and which cannot 

 be expressed in calorific values ? There is no absurdity in such 

 a question, but so far no experimental result has established the 

 presence of a source of energy in man of a totally different nature 

 from the known energies. Science, therefore, cannot take this 

 speculation into account for the present, 



