ENERGY TRANSFORMATIONS IN LIVING MATTER 133 



and division of the cells of the growing embryo. As each stage is 

 reached, similar changes in the distribution of energy will occur as in 

 previous generations, for the new embryo will arrive at them with 

 the same distribution as in past generations of its store of energy, and 

 hence the same phases in the energy phenomena will repeat them- 

 selves, except in so far as these are modified by nutrition and en- 

 vironment in a secondary degree. 



In the process of growth, the oxidation of the food yields the 

 necessary energy, and then this is utilised in building up fresh 

 cellular material, in fabricating chemical substances for the use of the 

 cells, and in producing other forms of energy. Throughout the 

 wonderful cycle, the biotic energy retains certain intrinsic charac- 

 teristics derived from the fertilised ovum, and by the impress 

 given by these the process is directed. 



IV. The fundamental properties possessed by living matter of 

 irritability, contractility, and conductivity are all energy phenomena 

 characteristic of life, and nowhere manifested by the operation of 

 other forms of energy in non-living matter. While it is un- 

 doubtedly true that the exhibition of these properties in living 

 tissue is accompanied by manifestations of other forms of energy, 

 such as chemical change, electricity and heat, and indeed neces- 

 sarily must be, since the cell obtains the energy used in the pro- 

 duction and propagation of these changes from such non-biotic 

 forms of energy, yet the alterations in irritability are characterised 

 by phenomena which are not chemical, electrical, or caloric, and 

 cannot be placed under any of the known forms of non-biotic 

 energy. 



Take, as an example, the nerve impulse travelling along a 

 living nerve-fibre. A similar phenomenon cannot be reproduced 

 in any non-living structure, and while it is accompanied by an 

 electric wave which travels at the same rate, it cannot be held 

 that the electrical energy is the nerve impulse, any more than 

 that the chemical change or electric wave accompanying a muscle 

 contraction wave is the contraction wave itself; or, to choose an 

 example from energy transformation in non-living matter, that the 

 heat in the wire and magnetic field around it are the electric current 

 travelling along the wire. In many other manifestations of irri- 

 tability than the nerve impulse it is known that increased electrical 

 negativity is associated with increased physiological activity, and 

 hence the most logical view certainly is that the negative wave 

 accompanying the nerve impulse betokens a wave of increased irri- 



