CHAP. IX.] THE CONTKACTILE TISSUES. 419 



In this manner the theory of Hermann brings together all the 

 chemical facts of muscular contraction : but it has the further merit 

 of attempting to solve the electrical facts also. It is entirely beyond 

 the scope of this work to explain in detail how this is accomplished. 

 It will be sufficient to state that the key to the most complicated 

 electrical phenomena of resting and acting muscle is to be found in 

 the contact of heterogeneous substances; and that the heterogeneity 

 required by the theory is supplied by the chemical difference which 

 undoubtedly exists between resting muscle on the one hand, and dying 

 or contracting muscle on the other. Bat, while the theory is so far 

 satisfactory, we must not blind ourselves to the capital imperfection of 

 it, that it does not represent to us how contraction itself takes place. 

 To suppose that in the hypothetical formation of gelatinous myosin 

 the physical particles of muscle are drawn together or suffer a 

 rearrangement, is but to support one hypothesis by advancing another ; 

 the explanation of muscular contraction on the view that it is 

 due to the shortening of gelatinous myosin has always appeared to 

 us improbable, and it is certainly not countenanced by any known 

 facts. 



272 



