6 ENERGY TRANSFORMATIONS 



mechanical energy, or vice versd. Similarly, for radiant light and 

 heat some bodies are transparent, and transmit these forms of 

 energy unaltered, while others are opaque and transform the 

 energy into other forms. 



It is not necessary to go on multiplying examples, but it may 

 be urged that in exactly similar fashion the protoplasm of the 

 living cell of plant or animal is on account of its peculiar struc- 

 ture and constitution a transformer of energy, specially adapted 

 for the intermediate conversion of chemical energy, presented in 

 certain suitable forms, into biotic energy, and for its final con- 

 version into other forms, such as mechanical energy and heat. 



A consideration of the forms of energy recognised as different 

 in the non-living world shows us that the only criterion of differ- 

 ence in type is the existence for each type of energy of a set of 

 phenomena peculiar to it, and the production by the play of the 

 particular form of energy of results typical of it, which cannot 

 be produced, at any rate under like conditions of operation, by 

 any of the other forms of energy. 



It is no argument against the existence of a discrete form of 

 energy that it is only produced from other forms of energy and 

 passes back again into other forms. In fact, it must be so pro- 

 duced and so pass back, or the balance of which the law of con- 

 servation of energy is the expression would be upset. Hence the 

 facts that vital phenomena arise from the expenditure in the cell 

 of chemical energy, and that the phenomena are accompanied by 

 development of heat, electricity, and other forms of energy are no 

 arguments that such vital phenomena are not characteristic of a 

 type of energy found only in living structures. 



It is only necessary to prove that a set of energy phenomena 

 exist in living structures which are characteristic of life, that 

 energy effects are produced and can be demonstrated in living 

 cells which cannot be shown apart from life, in order to prove 

 that we here have to deal with a type of energy which does not 

 appear in non-living matter. 



We may pass, accordingly, to an enumeration of some of the 

 peculiar energy properties of living matter upon which reliance 

 can be placed as proving that such matter is a peculiar energy- 

 transformer in which a peculiar type of energy (biotic energy) is 

 developed alongside of other forms which also occur in inorganic 

 nature. 



