Ixviii INTRODUCTION 



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" Whenever we abandon nature, and give ourselves up to 



the fantastic flights of our imagination, we become lost in 



vagueness and our efforts culminate only in errors. The 



only knowledge that it is possible for us to acquire is and 



always will be confined to what we have derived from a 



continued study of nature's laws ; beyond nature all is 



bewilderment and delusion : such is my belief." ^^ 



I ^'^ Lamarck thus afi&rms the mechanistic position, but he 

 goes on to say that the " exciting cause " is composed of 

 two factors, caloric and electricity. These he regarded as 



1/ subtle, invisible fluids which penetrate every part of the 

 organism. Its hfe is mainly due, he says, to caloric, and 

 its active movements to the electric fluid, or, in the case 

 of the more complex, to the galvanic fluid. These fluids 

 may indeed be somewhat specialised within the organism, 

 and other subtle invisible fluids may co-operate with them, 

 but Lamarck looked upon it as quite certain that they 

 were the chief components of the exciting cause, that en- 

 dows bodies with life. "Now this exciting cause is obviously 

 analogous to those spiritual factors, which Lamarck is so 

 careful to exclude. It is descended directly from the 

 " animal spirits " of more ancient writers, like Galen, and 

 it has strong vitalistic implications ; he goes so far as to 

 refer to heat, the most important of the subtle, invisible 

 fluids, as the " material soul of living bodies." Yet we 

 must remember that the so-called subtle, invisible fluids 

 were recognised by the physics of Lamarck's day. When 

 invoking the aid of these fluids for the explanation of physio- 

 logical phenomena, he was drawing on what he beheved to 

 be a purely physical source, and he constantly impresses upon 

 the reader that his explanations are exclusively physico- 

 chemical. The fact is that physics was at that time 

 imperfectly differentiated from metaphysics : Lamarck de- 

 rived his " exciting cause " from metaphysical elements, 

 which have since been entirely discarded : and he fell into 

 a semi- vitalistic mode of explanation, in spite of his desire 

 to keep free from it. Lamarck comes nearest to the modern 



