Ill SCIENCE AND PSEUDO-SCIENCE 119 



lacked these qualifications would feel tempted to 

 charge me with error. It appears that my sim- 

 plicity is greater than my powers of imagination. 

 The Duke of Argyll may not be aware of the 

 fact, but it is nevertheless true, that when a man's 

 arm is raised, in sequence to that state of con- 

 sciousness we call a volition, the volition is not the 

 immediate cause of the elevation of the arm. On 

 the contrary, that operation is effected by a certain 

 change of form, technically known as " contraction " 

 in sundry masses of flesh, technically known as 

 muscles, which are fixed to the bones of the 

 shoulder in such a manner that, if these muscles 

 contract, they must raise the arm. Now each of 

 these muscles is a machine comparable, in a 

 certain sense, to one of the donkey-engines of a 

 steamship, but more complete, inasmuch as the 

 source of its ability to change its form, or contract, 

 lies within itself. Every time that, by contracting, 

 the muscle does work, such as that involved in 

 raising the arm, more or less of the material which 

 it contains is used up, just as more or less of the 

 fuel of a steam-engine is used up, when it does 

 work. And I do not think there is a doubt in the 

 mind of any competent physicist, or physiologist, 

 that the work done in lifting the weight of the arm 

 is the mechanical equivalent of a certain proportion 

 of the energy set free by the molecular changes 

 which take place in the muscle. It is further a 

 tolerably well-based belief that this, and all other 



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