SCIENCE AND MAN. 347 



which would raise the temperature of an ounce of water 

 somewhat more than one degree Fahrenheit. I liberate 

 the weight: it falls to the earth, and by its collision 

 generates the precise amount of heat missing in the 

 muscle. My muscular heat is thus transferred from its 

 local hearth to external space. The fuel is consumed 

 in my body, but the heat of combustion is produced 

 outside my body. The case is substantially the same 

 as that of the Voltaic battery when it performs external 

 work, or produces external heat. All this points to the 

 conclusion that the force we employ in muscular exer- 

 tion is the force of burning fuel and not of creative 

 will. In the light of these facts the body is seen to be 

 as incapable of generating energy without expenditure, 

 as the solids and liquids of the Voltaic battery. The 

 body, in other words, falls into the category of ma- 

 chines. 



We can do with the body all that we have already 

 done with the battery heat platinum wires, decompose 

 water, magnetise iron, and deflect a magnetic needle. 

 The combustion of muscle may be made to produce all 

 these effects, as the combustion of zinc may be caused 

 to produce them. By turning the handle of a magneto- 

 electric machine a coil of wire may be caused to rotate 

 between the poles of a magnet. As long as the two 

 ends of the coil are unconnected we have simply to 

 overcome the ordinary inertia and friction of the ma- 

 chine in turning the handle. But the moment the two 

 ends of the coil are united by a thin platinum wire a 

 sudden addition of labour is thrown upon the turning 

 arm. When the necessary labour is expended, its 

 equivalent immediately appears. The platinum wire 

 glows. You can readily maintain it at a white heat, or 

 even fu?e it. This is a very remarkable result. From 

 the muscles of the arm, with a temperature of 100, we 

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