208 



NATURE 



\yan. II, 1872 



charge, overrule the natural charge ? Will the artificial 

 charge^ thus larger in amount than the natural, produce a 

 o-rearer degree of elongation in the muscular fibre than 

 that which is natural to the fibre ? Will the contraction 

 following the discharge of this artificial charge be greater 

 in amount than that which is natural to the fibre, because 

 the elasticity of the muscle has freer play under these 

 circumstances ? These questions, and others also of a 

 like nature, are suggested by the experiment upon the 

 elastic band ; for not only does the band elongate 

 with the charge and shorten with the discharge, but the 

 elongation and shortening are manifestly in proportion 

 to the amount of the charge and discharge. Nor are these 

 questions unanswerable. On the contrary, answers may 

 be found in more ways than one— in the examination of the 

 phenomena of electrotonus more particularly ; and these 

 answers are in no way ambiguous in their meaning. 



In electrotonus are strange modifications of mus- 

 cular action. In electrotonus, too, as I have shown 

 elsewhere,* are strange modifications of the electric con- 

 dition of the parts, there being everywhere in the region 

 of anelcctrotonus a positive charge overflowing from the 

 positive pole of the battery employed in the production of 

 electrotonus, there being everywhere in the region of 

 cathelectrotonus a negative charge overflowing from the 

 negative pole of the same battery. In anelectrotonus 

 there is a positive charge, not only present, but at work ; 

 in cathelectrotonus there is a negative charge, not only 

 present, but at work. At work certainly, for as I have 

 shown, the movements of the needle of the galvanometer 

 characteristic of electrotonus are caused by the movement, 

 not of a vokaic current, but of these charges through the 

 coil of the instrument, the movement of cathelectrotonus 

 by the flow of the negative charge, that of anelectrotonus 

 by the flow of the positive charge. At work also, as I have 

 also shown, in modifying muscular action. At all events, 

 the presence of a positive charge in anelectrotonus and 

 of a negative charge in cathelectrotonus are facts, and 

 therefore I am justified in looking to the phenomena of 

 muscular action in the two electrotonic states with a view 

 to find answers to the questions now under consideration. 

 At the onset of the inquiry, however, a grave difficulty 

 has to be coped with — a difficulty as to facts, for the 

 actual facts are not what they are believed to be. In a 

 word, it is not true that the action of anelectrotonus upon 

 muscular action is essentially different from that of cath- 

 electrotonus. Differences there are no doubt, but not any 

 that will prove to be of moment in the present place. It 

 is a fact that muscular action is suspended, not in anelec- 

 trotonus only, but in cathelectrotonus as well as in 

 anelcctrotonus. It is a fact that muscular i-ioiioalion is a 

 phenomenon common to both electrotonic states. Nor are 

 these the only points in the history of electrotonus which 

 require to be looked into carefully. So that, before pro- 

 ceeding further in this matter, it is necessary to ascertain 

 what are the facts which have here to be dealt with. 



The true history of muscular action during electro- 

 tonus may be well seen in the gastrocnemius of a frog by 

 means of certain experiments for the exhibition of which 

 the apparatus already used in the experiment with the 

 elastic band is furnished with certain parts which have yet 

 to be described. These parts consist of a pillar and a 

 platform resting upon it horizontally, the pillar rising from 

 the side of the stand opposite to that occupied by the 

 charging and discharging rods. The pillar has a telescope 

 arrangement, by which its length may be altered, and a 

 screw-collar, by which it may be fixed at any length. The 

 platform consists of a four-sided metal floor, five inches 

 in length by three in breadth, with a narrow and rather 

 thick border of ebonite in which are two binding screws 

 for holding electrodes upon each of its sides, with a long 

 roller at one of its ends, and with a moveable gutta percha 

 cover of such a shape and size as to allow it to be slipped on 

 • "Dynamics of Nerve and Muscle." Macmillan, 1870.'.' 



and off between the ebonite borders, and fixed when on 

 by having its edges made to play under the hollowed-out 

 inner margins of the borders. In the actual experiment 

 what has to be done is — to remove the elastic band and 

 the weights attached to it — to fix the platform, so that it is 

 a little behind and above the level of the driving-wheel, 

 with the end to which the roller is attached turned towards 

 this wheel — to fix the wires from the battery and induction 

 apparatus to the binding-screws on the platform, the 

 wires from the battery being carried to the side on which 

 the screws are farthest from the roller (the battery, I 

 should have said, consists offour medium-sized Bunsen- cells, 

 and the induction-apparatus is one in which the secondary 

 coil may be slipped altogether away from the primary — a 

 Du Bois-Reymond's inductorium, in fact), — to prepare a 

 frog's hmb by stripping off the skin and dissecting away 

 all parts of the thigh except the sciatic nerve, — to remove 

 the gutta-percha cover from the platform, and pin upon it 

 the prepared limb with its heel close to one end, care 

 being taken not toinjure the nerveor musclein doing this, — 

 to tie to the tendo-achillis the string which belongs to the 

 weights, — to put back the gutta-percha cover into its place 

 with the limb thus pinned and arranged upon it, the string 

 attached to the tendo-achillis being brought out over the 

 end which comes next to the roller,— to carry this string 

 over the driving-wheel to the rod carrying the weights, — 

 and to adjust these weights so as to put the gastro- 

 cnemius gently on the stretch, — and lastly, to draw out the 

 nerve, and carry it first across the electrodes belonging to 

 the induction-apparatus and then across those belonging 

 to the battery, these electrodes, to allow of this, being 

 made to point inwardly to a sufficient distance across the 

 platform, two from one side, two from the other. In this 

 way, when the circuits are closed (they are open at first) 

 the nerve may be acted upon by voltaic and faradaic elec- 

 tricity as in an ordinary experiment in electrotonus. In 

 this way, any change in the length of the gastrocnemius 

 must tell upon the index, just as the changes in the length 

 of the elastic band were made to tell, only in the con- 

 trary direction. 



These arrangements being made, two experiments have 

 to be tried, the one for exhibiting the action of anelectro- 

 tonus upon the gastrocnemius, the other for exhibiting 

 that of cathelectrotonus, and each differing from the 

 other only in the relative position of the voltaic poles, the 

 positive pole being next to the insertion of the nerve into 

 the muscle in analectrotonus, the negative pole being in 

 this position in cathelectrotonus. 



In the experiment for exhibiting the action of anelectro- 

 tonus upon the muscle — that with the positive pole in the 

 position next to the insertion of the nerve into the muscle 

 — there are three distinct steps, the first taken before 

 setting up the state of anelectrotonus, the two others after 

 this time. 



The first step, or that which is taken before the esta- 

 blishment of anelectrotonus, is to tetanise the muscle with 

 faradaic currents only just strong enough to act upon the 

 muscle at all in this way. In this case the circuit of the 

 induction-apparatus is closed, but not that of the voltaic 

 battery, and therefore the nerve is acted upon by faradaic 

 currents before the establishment of anelectrotonus. At 

 first, the faradaic currents used arc strong enough to 

 tetanise the muscle effectually ; then these currents are 

 weakened by drawing away the secondary coil from the 

 primary until the tetanus comes to an end ; last of all, the 

 tetanus is brought back again to the very slightest degree 

 by moving the secondary coil back again towards the 

 primary coil, and leaving it at the point where the currents 

 produced in it just begin to have a tetanising action. This 

 is the first step in the experiment. 



The second step consists in the establishment of an- 

 electronus while the nerve is still being acted upon by 

 these feeble faradaic currents. Hitherto the circuit of the 

 induction apparatus was closed, while that of the voltaic 



