60 BULLETIN OF THE 



down into carbon dioxide, lactic acid, (Fleischmilchsaure,) and 

 gelatinous myosin. The rearrangement of molecules necessary to 

 produce the latter body determines the contraction. Subsequently 

 the gelatinous myosin combines with the necessary materials fur- 

 nished by the blood, and becomes inogen again. This decomposi- 

 tion and recomposition goes on also while the muscle is at rest, but, 

 as then the gelatinous myosin is reconverted into inogen as rapidly 

 as it is formed, no contraction results. 



Du Bois-Reymond declares all this to be merely unsupported hy- 

 pothesis. 24 Gamgee himself admits that it is, after all, not very 

 clear why the gelatinous myosin should contract. Michael Foster, 25 

 who wholly rejects this particular chemical hypothesis, nevertheless 

 seems quite sure that the true explanation will be found to be a 

 chemical one. He insists that muscular contraction is essentially 

 a translocation of molecules, and declares that whatever the 

 exact way in which this translocation is effected may be, it is funda- 

 mentally the result of a chemical change, or, as he describes it, "an 

 explosive decomposition of certain parts of the muscle-substance." 



The purpose I have in view does not require, fortunately, that I 

 should attempt to decide whether these more purely chemical 

 theories of muscular contraction, or the more purely electrical theo- 

 ries, are best entitled to confidence. My object has been effected, 

 if I have impressed you with the fact that wide differences of opinion 

 still exist as to the nature of the process, and that further investi- 

 gation is indispensable for the settlement of existing controversies. 



The subject just briefly discussed briugs us naturally to the con- 

 sideration of the nature of the action of the motor nerves, by 

 which, in all animals possessed of a muscular and nervous system, 

 the contraction of the muscles is regulated and determined. 



The hypothesis which identifies the nervous currents with elec- 

 tricity was propounded in the posthumous work of Hausen 26 in 

 1743, and, notwithstanding all the difficulties and objections it has 

 encountered, still survives in a modified form in many contempora- 

 neous minds. Those who hold to this view appeal in its support to 

 the electrical phenomena actually observed in nerves in accordance 

 with the investigations of Du Bois-Reymond. These observations 

 have long been widely accepted as conclusive proof that natural 

 currents exist in the quiescent nerve of the same general character 

 as those attributed to the quiescent muscle, which I outlined a few 

 minutes ago. The electro-motive force of this current was found 



