18 THEORIES OF LIFE. [iNTROD. 



deputed " to control and direct" its organization, development, and 

 growth ? 



The modern advocates of this doctrine have been driven to its 

 adoption, from the difficulty (or, as they conceive, the impossibility) 

 of explaining the phenomena of organization and life on principles 

 analogous to those on which the changes of inorganic matter may 

 be accounted for : this difficulty consisting in the supposed existence 

 of certain differences in the mode of combination of the elementary 

 constituents of organic and inorganic compounds, seconded by the 

 fact, of the synthesis of organic compounds having hitherto baffled 

 the chemist's art. It has puzzled them to think that out of the 

 same elementary and proximate principles, so infinite a variety of 

 animals and plants could be formed ; and Dr. Prout has been espe- 

 cially staggered by the fact, that carbon and water, which contri- 

 bute so largely to the formation of various organisms, have never, 

 although aided by heat, light, and electricity, when out of an 

 organized body, and left entirely to themselves, been able to unite, 

 either in virtue of their own properties or from accident, so as to 

 form any plant or animal, however insignificant. 



In the first place, let it be observed, that many of the phenomena 

 of life may be accounted for on physical or chemical principles. 

 The changes effected in the air and in the blood by respiration, the 

 phenomena of absorption, and, in some degree, those of secretion, 

 are the results of purely physical processes. It is in the highest 

 degree probable that many of the actions of the nervous system are 

 due to physical changes in the two kinds of nervous matter, sub- 

 stances of complex constitution and high equivalent number, and 

 therefore prone to change. Stomach-digestion is now known to be 

 a chemical solution ; the generation of heat is due to the same 

 chemical phenomenon as will give rise to it in the inorganic world ; 

 and electricity is also similarly developed within the body. How 

 entirely dependent on physical changes are the senses of vision and 

 hearing, and how completely are their organs adapted to the laws 

 of light and sound? And, doubtless, a further insight into the 

 nature of the various organic processes will reveal to us a closer 

 analogy between the laws by which the two great kingdoms of 

 nature are governed. 



Nor is there so great a chasm between matters organic and in- 

 organic, as to chemical composition, as some would have us believe. 

 It has already been shewn that modern chemical research tends to 

 prove a similarity as regards the mode of combination of the 

 elements in both ; and the labours of chemists have been crowned 



