PHYSIOLOGY Ixix 



vitalistic writers when he attempts to describe the physiology 

 of the nervous impulse. He attributes it to a "nervous 

 fluid," and this, he says, is no other than electric fluid which 

 becomes modified and " animaUsed " on entering into the 

 bodies of the higher animals. 



By what reasoning did Lamarck reach this conclusion ? 

 The facts before him consisted mainly in the rapid trans- 

 mission of some kind of impulse from or to the brain from 

 remote regions of the body. Lamarck considers how this 

 transmission could be accompHshed : he passes in review 

 all possible alternatives : Eicherand had refuted the sugges- 

 tion that some vibration of the nerves conveyed the mysterious 

 impulse : there remained only two possible alternatives : 



(1) that the impulse should be carried by the visible or 

 " essential " fluids of the animal, such as blood and lymph ; 



(2) that it should be carried by invisible fluids analogous or 

 identical with the electric, galvanic and magnetic fluids. 

 The first alternative is ruled out by many facts : in the 

 first place no such movement of the visible fluids can be 

 detected in nervous action : in the second place, the visible 

 fluids are too gross and heavy to move with the required 

 velocity, which Lamarck affirms (quite wrongly of course) to 

 be nearly equal to that of light : and so on. All conceivable 

 alternatives being thus ruled out, it follows, says Lamarck, 

 that the one remaining unrefuted possibility must be the 

 true explanation : there must be a subtle, invisible fluid of 

 the character named above. 



Now I wish to point out that this argument is identical 

 in every particular with that by which Hans Driesch and all 

 other vitahsts of our time prove the existence of a vital force. 

 Driesch names the argument per exclusionem. Like Lamarck, 

 he takes three or four conceivable alternatives ; though -I 

 need hardly say that the conceivable alternatives of to-day 

 are radically different from the conceivable alternatives of 

 a hundred years ago. He then refutes all possible alterna- 

 tives but one : and thereupon announces that that one (the 

 vital or spiritual force) is the true explanation, conferring 



