CHAPTER I. 



ORGANIC MATTER. 



% 1. Of tlie four chief elements which, in various com- 

 binations, make up living bodies, three are gaseous. While 

 carbon is known only as a solid, oxygen, hydrogen, and 

 nitrogen are known only in the aeriform state. Under 

 pressures great enough to reduce them almost to the density 

 of liquids these elements have still defied all efforts to liquefy 

 them. There is a certain significance in this. When we 

 remember how those re- distributions of Matter and Motion 

 which constitute Evolution, structural and functional, imply 

 motions in the units that are re-distributed ; we shall see a 

 probable meaning in the fact that organic bodies, which 

 exhibit the phenomena of Evolution in so high a degree, are 

 mainly composed of ultimate units having extreme mobility. 

 The properties of substances, though destroyed to sense by 

 combination, are not destroyed in reality : it follows from the 

 persistence of force, that the properties of a compound are 

 resultants of the properties of its components — resultants in 

 which the properties of the components are severally in full 

 action, though greatly obscured by each other. One of the 

 leading properties of each substance is its degree of molecular 

 mobility ; and its degree of molecular mobility more or 

 less sensibly affects the molecular mobilities of the various 

 compounds into which it enters. Hence we may infer some 

 relation between the gaseous form of three out of the four 



