Dr. RadcliflFe on Muscular Action. 389 



The interpretation is that tlie reactions during muscular contraction 

 are, not between the immary nerve-current and the muscular cur- 

 tent, but between the muscular current and the secondary or iyulured 

 currents which may be supposed to spring into existence when the 

 primary or inducing nerve- current is suspended or renewed. The 

 fact that the nerve-current sinks during contraction, is appealed to 

 as an argument that the primary nerve-current is actually suspended 

 and renewed during muscular contraction, and that in this manner 

 the occasions for the appearance of the secondary or induced cur- 

 rents are thus properly provided for. It is pointed out that the 

 reactions between the uninterrupted nerve-current and the muscular 

 current, and between the muscular current and the induced or se- 

 condary currents which come into play when the primary or inducing 

 nerve-current is interrupted or renewed, must be altogether diiFerent. 

 With respect to the reactions which take place between the uninter- 

 rupted nerve-current and the muscular current, there is reason to 

 believe that these must result in mutual intensification, for the nerve- 

 current and the muscular current pass in the same direction. At any 

 rate this is the case in the hind-limbs of the frog, or the fore-limbs 

 of the same animal, and in the hind-limbs of the rabbit, dog, cat, and 

 mouse. With respect to the reactions which take place between the 

 muscular current and the secondary currents -which come into play 

 when the primary or inducing nerve-current is suspended or renewed, 

 there is every reason to believe that the result is altogether different. 

 In this case, it appears as if the secondary or induced current must 

 involve, not the intensification, hut the discharge of the muscular 

 current in all the muscle which enters into the circuit of the second- 

 ary current. For what is the peculiarity of the secondary current ? 

 It is a current of momentary duration, disappearing almost in the 

 very instant of its appearing, and carrying along with it in its dis- 

 charge any electricity it may meet with in its circuit. Hence there 

 is no difficulty in understanding why the galvanometer should afford 

 evidence of abatement of the muscular current at the moment when 

 the nerves are concerned in producing muscular contraction. Nor 

 is there any difficulty in understanding how contraction should be 

 brought about by this action of the nerves, if, as there has seemed 

 some reason to believe, muscular contraction is antagonized by the 

 presence of the muscular and nerve-currents. 



The author proceeds, in the next place, to consider the pheno- 

 mena which attend upon the action of the ordinary galvanic current 

 upon the muscular current. In this part it is pointed out that there 

 is the same broad line to be drawn between the effects of the 

 primary galvanic current and of the secondary currents which spring 

 into existence when the inducing or primary current is suspended 

 or renewed, and by keeping this distinction in mind it is shown that 

 an intelligible physical reason may be obtained for the differences of 

 the "direct" and "inverse" currents for "voltaic alternatives," 

 and so on. The argument is complicated and not easily reducible 

 to a few words ; it requires, moreover, certain diagrams which 

 cannot l)c used in tliis abstract ; and therefore we will only say that 

 the conclusion to which it leads, is that there must be a distinct an- 



