22 INTRODUCTION. I.ECT. I. 



tricky, and attraction ? Such an inference would be as far 

 from the truth as the conclusion of those who have denied 

 and still deny these general properties to living beings, and 

 who regard them as entirely beyond the influence of phy- 

 sical agents. 



Examine those phenomena of living bodies, which, if I 

 may be permitted so to call them, are the most physical, the 

 most chemical, and you will find considerable differences in 

 the mode of action of physical and chemical agents in the 

 organism, differences which are inexplicable in the present 

 state of our knowledge of the laws governing these forces. 

 Does not the phenomenon of vision itself, which may be 

 termed a purely physical phenemenon, present peculiarities 

 which remain up to the present moment unexplained? If 

 the latest discoveries in science enable us to account for 

 the distinctness of vision at all distances, and the absence 

 of colour on the edges of the image, how, by the aid of phy- 

 sical laws, can we explain the perception of a single object 

 in its natural position, by a double and inverted image ? 

 What could we not say of hearing and the voice, which are 

 simply effects of some particular vibrations of the air, propa- 

 gated by solids, according to the general laws of acoustics? 

 To questions such as these science can give no completely 

 satisfactory answer. 



Organization. The chemical action of light, which de- 

 composes carbonic acid, carries the carbon under the form 

 of new combinations into the interior of vegetables, disen- 

 gages the oxygen, and thus produces what the most pow- 

 erful chemical affinities cannot accomplish, is certainly dif- 

 ferent from that which decomposes some oxides and me- 

 tallic chlorides, an effect for the production of which the 

 feeblest chemical actions are sufficient. Apply an electric 

 current to the nerves of a living animal, and the peculiarity 

 of the resulting phenomena will prove to you the immense 



