IX.] MUSCULAR ACTION AND HEAT. 109 



NOTE. 

 ON THE RELATION OP MUSCULAR ACTION TO HEAT. 



We have seen that in muscular contraction heat is produced; 

 and this I believe to be, in part, transformed vital energy. (I 

 say in part, because I have no doubt that it is in part also due 

 to the chemical action that takes place in the muscle at the 

 moment.) 



But it has been shown by careful experiments on frogs, that Cold pro- 



the first effect of muscular contraction is a sUsht cooling. ^ The °-^^^^^ ™ 



° ° muscular 



most probable explanation of this fact appears to be, that the action, 

 commencement of muscular action causes the conversion of a 

 small quantity of heat into muscular motor energy. 



There is a remarkable fact in inorganic dynamics, which is 

 nearly parallel to this. 



If a joint formed by soldering bismuth to antimony is heated, Parallel 

 an electric current will flow through the joint from the bismuth ^^ ^^ 

 to the antimony. This dejiends on the unequal powers of the electricity, 

 two metals as conductors of heat. 



If a current from an external source is sent through the joint 

 from the bismuth to the antimony (consequently in the same 

 direction as the current that would be produced by heating the 

 joint), the joint will be cooled. If the current is sent through 

 the joint in the opposite direction, the joint will be heated.^ 



The only possible explanation of the cooling of the joint is, 

 that the passage of the electric current through it determines 

 the conversion of part of its heat into electricity ; and this is 

 analogous to the commencement of muscular action determining 

 the conversion of part of the heat of the muscle into muscular 

 motor energy. 



Uoth of these cases are exceptional. They are, I believe, the These 

 only known instances of the conversion of heat into any other ^^ntt^^^ 

 form of energy being caused by the passage of a current of tional. 

 that other form of energy. 



1 Solger, and Meyerstein and Thiry, quoted in the Medico-Chirurgical 

 Eeview, January 1864. 

 * Tyndall, in the Philosophical Magazine, December 1852. 



