THE LIVING WORLD 239 



to the future. But every living creature, at every stage 

 of its existence, regards both the past and the future, and 

 thus lives continually in a definite relation to both of 

 these, as well as to the present. It has, therefore, under 

 the conditions necessary for life, a definite spontaneous 

 activity of its own. An inorganic body may be one kind 

 of substance, but it is only a living organism which can 

 be called an individual. As yet science has not afforded 

 us any means whereby we may give origin to life 

 whereby we may change any non-living substance into 

 a being instinct with life. 



Plants possess the power of performing all the functions 

 essential to continued life namely, alimentation, circula- 

 tion, respiration, secretion and generation. They give 

 no evidence, however, of possessing any true power of 

 sensation. The movements of the sensitive plant, the 

 sun-dew, Yenus's fly-trap, &c., are very wonderful, but 

 the most careful examination of those plants has not 

 discovered any nervous tissue in them. As this is the 

 essential and only organ of feeling which organisms are 

 known to possess, its absence in plants justifies our 

 denying them the power of sensation. To say that our 

 ordinary domestic plants our potatoes, and our cabbages 

 really feel, would be absurd in the eyes of men of 

 common sense. 



The movements of plants are also effected in a different 

 manner from those of animals. In the latter it takes 

 place by the aid^of muscular tissue, a substance which 

 has not yet been found in any plant, and it is a 

 rule, gathered from long experience, that "structure" and 

 " function," in organisms, vary together. 



As already pointed out, no animal can live without 

 feeding, directly or indirectly, upon plants, since they 

 alone possess the power of building up organic matter 



