LIFE AND ORGANISATION. 51 



itself include the greatest of all the problems submitted to 

 human thought. All distinctions and diversities are trifling 

 in comparison with the one line, which separates inanimate 

 matter from those living organisms created out of it ; with 

 properties and powers of endless variety; and, above all, 

 endowed with that wonderful power of reproduction, which 

 maintains the continuity of the species while individual forms 

 are successively passing away. No step so vast as this, no 

 mutation so wonderful, in any part of creation. The mys- 

 tery is not solved scarcely lessened to our conception by 

 those researches which, descending in the scale of existence, 

 seem to obliterate all certain distinction between animal and 

 vegetable life, and to bring the latter to the very lowest grade 

 to which the term living can fitly be applied. It is still the 

 distinction between that which can reproduce itself and that 

 which cannot; and in this single condition lies the clearest 

 expression of all vitality, whatsoever its form or degree. No 

 definition of life can be complete without it. Alone it suffices 

 to mark that line of division which even the finest microscope 

 fails to reach ; and it applies no less to that more wonderful 

 and complex animal machinery by which the higher forms 

 of existence are maintained and perpetuated. 



Into this domain of organic life modern science has pene- 

 trated with not less zeal and success than have signalised it 

 in the other branches of physical science, notwithstanding 

 certain distinctions which may seem to favour the pursuit of 

 the latter. Such are the surpassing grandeur of the various 

 discoveries in inorganic nature ; the mathematical certainty 

 of many of the laws thence derived ; and the important prac- 

 tical uses to which these discoveries have been applied, en- 

 larging the dominion of man over nature through elements 

 which were formerly known but as objects of admiration or 

 terror. No period has been so prolific of these achievements 

 as that in which we are now living. 



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