2 THE LIVING AXD THE DEAD BODY. 



The characteristic of the dead body then is that, being a mass 

 of substances of considerable potential energy, it is always more 

 or less slowly losing energy never gaining energy ; the capital of 

 energy present at the moment of death is more or less slowly 

 diminished, is never increased or replaced. 



3. When on the other hand we study a living body we are 

 struck with the following salient facts. 



1. The living body moves of itself, either moving one part of 

 the body on another or moving the whole body from place to place. 

 These movements are active ; the body is not simply pulled or 

 pushed by external forces, but the motive power is in the body 

 itself, the energy of each movement is supplied by the body itself. 



2. These movements are determined and influenced, indeed 

 often seem to be started, by changes in the surroundings of the body. 

 Sudden contact between the surface of the body and some foreign 

 object will often call forth a movement. The body is sensitive to 

 changes in its surroundings, and this sensitiveness is manifested 

 not only by movements but by other changes in the body. 



3. It is continually generating heat and giving out heat to 

 surrounding things, the production and loss of heat, in the case 

 of man and certain other animals, being so adjusted that the 

 whole body is warm, that is, of a temperature higher than that 

 of surrounding things. 



4. From time to time it eats, that is to say, takes into itself 

 supplies of certain substances known as food, these substances 

 being in the main similar to those which compose the body and 

 being like them chemical bodies of considerable potential energy, 

 capable through oxidation or other chemical changes of setting 

 free a considerable quantity of energy. 



5. It is continually breathing, that is, taking in from the 

 surrounding air supplies of oxygen. 



6. It is continually, or from time to time, discharging from 

 itself into its surroundings so-called waste matters, which waste 

 matters may be broadly described as products of oxidation of the 

 substances taken in as food, or of the substances composing the 

 body. 



Hence the living body may be said to be distinguished from 

 the dead body by three main features. 



The living body like the dead is continually losing energy 

 (and losing it more rapidly than the dead body, the special 

 breathing arrangements permitting a more rapid oxidation of its 

 substance), but unlike the dead body is by means of food contin- 

 ually restoring its substance and replenishing its store of energy. 



The energy set free in the dead body by the oxidation and 

 other chemical changes of its substance leaves the body almost 

 exclusively in the form of heat, whereas a great deal of energy 

 leaves the living body as mechanical work, the result of various 

 movements of the body ; and as we shall see a great deal of the 



