CHAPTEE I. 



OEGANIC MATTER. 



§ 1. Of the four chief elements which, in various com- 

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

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

 nitrogen habitually maintain the aeriform state. Only by 

 intense pressures joined with extreme refrigerations have 

 two out of the three (some say all) been reduced to the liquid 

 form. 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 



