276 VOLKMANN'S ELECTEICAL EXPERIMENTS. 



1st. When a continuous electrical current is passed along a centrifu- 

 Voikmann's g a ^ nerve, contraction of the muscles which that nerve supplies 

 results. takes place, and continues as long as the electric current pass- 

 es, without relaxation, but ceases the moment the current is stopped. 



2d. When a continuous electric current is passed through a ganglion, 

 contraction of the muscles supplied by the centrifugal nerves of that gan- 

 glion ensues. These contractions do not .alternate with relaxation, and 

 on stopping the current the contraction does not cease as in the preced- 

 ing case, but is continued for a period of time. 



3d. When a continuous electric current is passed down a centripetal 

 nerve, muscular contraction of the parts supplied by the corresponding 

 centrifugal nerves occurs, and these contractions alternate with relax- 

 ations. 



In view of these facts, we are brought to two conclusions : First, that 

 there is a property in the ganglion which enables it to hold in reserve a 

 portion of the influence brought into it, so as to keep up the action for a 

 period of time after the original disturbing causes have ceased. Second, 

 that the structure of the ganglion is such as to permit the escape of the 

 coming influence by lateral ways, either periodically or otherwise, and so 

 to produce from a continuous influence an intermitting effect. 



Kecalling the fact that a ganglion is made up of nerve-tubes and vesi- 

 cles conjointly, these electrical results must find their solution in the el- 

 ementary structure of the ganglion, that is to say, in its vesicular por- 

 tion ; for it is not to be supposed that a current of electricity, such as we 

 are here considering, would ever have an opportunity of escaping from 

 the axis cylinder along which it passes. The isolating quality of the 

 white cylinder of Schwann would prevent any such effect. It is not nec- 

 essary that we should embarrass ourselves here with the fact that elec- 

 tric currents of sufficient intensity could make their way out from the in- 

 terior channel in spite of its insulating investiture, since it is only with 

 those of a far less power that we have to deal. Arrived in the vesicle, 

 the current at once diffuses itself throughout the granular material, just 

 in the same manner that it would diffuse throughout a spherical conduct- 

 ing mass if brought to it by a wire, and escape therefrom through any 

 number of similar wires that might chance to be in contact with the con- 

 ducting mass beyond ; and though the main body of the current would, 

 as may be readily proved, under these circumstances move in a direct 

 line from the point of entry to the point of exit, there would be neverthe- 

 less a diffusion of part of it through the conducting mass, no portion 

 thereof remaining unaffected. In a good conductor, such as a metal, this 

 laterally diverging current would instantly escape, but the case becomes 

 very different in the less perfectly conducting material, the granular sub- 

 stance within the cell. As in the secondary piles of Bitter, which, when 



