GENEEAL PAST. 



CHAPTER I. 



ORGANISED AND UNORGANISED SUBSTANCES. 



IN the world, which is perceptible to our senses, we distinguish 

 between living organised and lifeless unorganised bodies. The 

 former (i.e., animals and plants) are endowed with the power of 

 movement, and they remain the same in spite of manifold changes 

 both of themselves as a whole and of their parts, and in spite of 

 continual change of the matter entering into their composition. 

 Unorganised bodies, on the other hand, are found in a condition 

 of constant rest ; and although this rest is not necessarily fixed and 

 unchangeable, yet they are without that independence of movement 

 which manifests itself in metabolism. In the former we recognize an 

 organisation, a composition of unlike parts (organs), in which the 

 matter exhibits its activity in a fluid and dissolved form; in the 

 latter we meet with a mass which is more uniform, though as far 

 as the position and arrangement of the molecules are concerned, 

 not always homogeneous, and in which the various parts continue 

 in a state of resting equilibrium so long as the unity of the body 

 remains undisturbed. The matter of unorganised bodies (for in- 

 stance, of crystals) is in a state of stable equilibrium, while through 

 the organised being a stream of matter takes place. 



The properties and changes of living bodies are strictly dependent 

 on the physico-chemical laws of matter, and this is recognized more 

 clearly as science advances; yet it must be admitted that we are 

 entirely ignorant of the molecular arrangement of the material basis 

 of a living organism, and it exists under conditions the nature of 

 which is as yet unexplained. These conditions, which we may 

 designate; as vital, without thereby calling in question their depen- 

 dence on material processes, distinguish organisms from all un- 



