INTRODUCTION. 



1. DISSECTION, aided by microscopical examination, teaches 

 us that the body of man is made up of certain kinds of material, 

 so differing from each other in optical and other physical characters 

 and so built up together as to give the body- certain structural 

 features. Chemical examination further teaches us that these 

 kinds of material are composed of various chemical substances, a 

 large number of which have this characteristic that they possess a 

 considerable amount of potential energy capable of being set free, 

 rendered actual, by oxidation or some other chemical change. 

 Thus the body as a whole may, from a chemical point of view, be 

 considered as a mass of various chemical substances, representing 

 altogether a considerable capital of potential energy. 



2. This body may exist either as a living body or (for a 

 certain time at least) as a dead body, and the living body may at 

 any time become a dead body. At what is generally called the 

 moment of death (but artificially so, for as we shall see the 

 processes of death are numerous and gradual) the dead body so 

 far as structure and chemical composition are concerned is exceed- 

 ingly like the living body ; indeed the differences between the two 

 are such as can be determined only by very careful examination, 

 and are still to a large extent estimated by drawing inferences 

 rather than actually observed. At any rate the dead body at 

 the moment of death resembles the living body in so far as it 

 represents a capital of potential energy. From that moment 

 (inwards however the capital is expended; by processes which 

 are largely those of oxidation, the energy is gradually dissipated, 

 leaving the body chiefly in the form of heat. While these chemi- 

 cal processes are going on the structural features disappear, and 

 the body, with the loss of nearly all its energy, is at last resolved 

 into " dust and ashes." 



