78 PRINCIPLES OF PHYSIOLOGY 



friction of a train of wheels. While the energy 

 is thus doing work it is said to be actual or 

 kinetic. The complete combustion of a 

 given amount of olein would produce a certain 

 equivalent of heat, and the heat, again, might 

 be transformed into a certain equivalent of 

 motion. There is a fixed quantitative rela- 

 tion between the two modes of energy. Thus 

 physical science tells us that a unit of heat is 

 the amount of heat that is required to raise 

 the temperature of 1 gramme (15.4324 grains) 

 from 15 to 16 centigrade, and the unit of 

 work is the grammetre, or the amount of work 

 expended in lifting 1 gramme to the height of 1 

 metre (39.37 inches). Apply this to a special 

 case ; a decomposition liberating heat, develops 

 1 heat unit, and this heat, if it does mechanical 

 work, will perform 424 grammetres of work. 

 Thus 1 unit of work may be converted into 

 1 unit of heat, and conversely. 



37. Energy therefore may be either potential 

 or kinetic. When simple substances are 

 combined to form complex ones, energy 

 becomes latent or potential, and when a 

 complex substance is split up into simpler 



