G 



ANIMAL MECHANICS. 



loss of latent heat, loss of statical electricity, and change of 

 chemical products from higher to lower forms, are all repre- 

 sentatives of force expended, or work done, it has been pro- 

 posed by various authors to select one or other of these ex- 

 ponents of work, as the means of measuring its amount under 

 various conditions. It seems to me that chemical transfor- 

 mations present the most certain and ready of all known 

 methods of determining the work done by the various tissues 

 of the body in the discharge of the several functions assigned 

 to them in the economy of nature. 



All these chemical, electrical, and calorifical changes are 

 intimately connected with the supply of fresh arterial blood to 

 the muscles ; and any theory of muscular action that does 

 not explain the necessity of such a fresh supply of blood must 

 be erroneous. 



On the electrical theory of muscular action, the contraction 

 of the muscle is accompanied by a loss of electrical tension, 

 causedby the partial discharge of the opposite electricities of the 

 outer and inner portions of the muscular bundles, and a supply 

 of fresh blood is admittedly necessary for the restoration of that 

 tension ; the contraction being supposed due to the molecular 

 attraction of the muscular particles when freed from the con- 

 trol of their induced electricity. This theory of muscular 

 action certainly commends itself by the explanation which it 

 affords of rigor mortis on principles analogous to those of or- 

 dinary muscular contraction ; but, inasmuch as no method has 

 been as yet devised for measuring the total loss of electrical 

 tension caused by a given amount of muscular action, it seems 

 to me that the electrical theory of such action must be re- 

 garded, in the present state of science, as a theory incapable of 

 yielding numerical results, which are the only tests to which 

 true science can submit its decisions. 



Of the other two exponents of work done, namely, the ca- 

 loric developed, or the urea, carbonic acid, and water produced, 



