206 



NATURE 



\yan. II, 1872 



ELECTROPHYSIOLOGICA : 



SHOWING HOW ELECTRICITY MAY DO MUCH OF WHAT IS 

 COMMONLY BELIEVED TO BE THE SPECIAL WORK OF A 

 VITAL PRINCIPLE 



II. 



2. How Ekctricily may do much of what is commonly 

 believed to be the work of a vital principle in muscular 

 action. 



I HAVE long held that a vital property of " irritability," 

 or "tonicity," was unnecessary in muscular action. 

 As it seemed to me, the state of relaxation in living muscle 

 was to be accounted for by the mutual repulsion of m.ole- 

 cules arising from the presence in the muscle at the time 

 of a charge of electricity, sometimes positive, sometimes 

 negative ; as it seemed to me, muscular contraction, 

 whether in ordinary muscular action or in rigor mortis, 

 was nothing more than the result of the operation of the 

 elasticity of the muscle upon the discharge, sudden or 

 gradual, of the charge which had previously kept up the 

 state of relaxation. And I still hold that the state of re- 

 laxation is caused by the presence in the muscle of a 

 charge of electricity, and that muscular contraction is 

 brought about by the elasticity of the muscle coming into 

 play upon the discharge of this charge ; but, since I began 

 to work with the new (Quadrant Electrometer of Sir Wm. 

 Thomson, I have been obliged to take a different view 

 of the way in which the charge operates in causing relaxa- 

 tion. The fact, discovered by means of this instrument, 

 that there are two chirges of electricity in muscle, positive 

 and negative, was fatal to the idea that the state of relaxa- 

 tion was due to the mutual repulsion of molecules conse- 

 quent upon the presence in muscle of a single charge, 

 positive or negative. With either charge singly the idea 

 might be entertained, though it was not easy to understand 

 how, wanting effectual insulation, the electricity could be 

 kept to its work ; with two opposite charges, on the con- 

 trary, the attraction of each charge for the other must 

 neutraHse the repulsion arising from the presence of either 

 singly. Nor did 1 find away of escape from this difficulty 

 until 1 began to seek it in a totally different direction, even 

 in the theory according to which the sheath of muscular 

 fibre during rest is charged as a leyden-jar is charged. 

 Is it possible, I asked myself, that the two opposite 

 charges, disposed leyden-jar-wise upon the two surfaces of 

 the sheath, may cause elongation of the fibre by com- 

 pressing between them the elastic sheath ? Opposite 

 charges of electricity must attract each other ; that was 

 plain enough. Opposite charges attracting each other 

 across an elastic sheath may compress that sheath in 

 such a way as to cause elongation of the fibre ; that was 

 not impossible. Upon this view, too, there was no difficulty 

 in understanding how each charge was prevented from 

 escaping, and made to work in this manner, by the mutual 

 attraction of each for the other. In a word, the idea that 

 the two charges might act in this way in causing muscular 

 relaxation was far more easy to realise than that which 

 regarded the state of relaxation as the result of the mus- 

 cular molecules being kept in a state of mutual repulsion 

 by the presence of one charge in the muscle. And so it 

 was that it became necessary to look into this matter a 

 little more closely — to put it to the test of experiment, as 

 best I could. 



In order to this, I began by inquiring whether the 

 idea in question was possible or not. I wanted to be 

 certain that the mutual attraction of two charges of 

 electricity, dispersed leyden-jar-wise upon the two surfaces 

 of the sheath of the fibre, would cause elongation, and 

 that the discharge of this charge would be followed by 

 contraction ; and, after several abortive attempts, I found 

 what I wanted, and more than I expected at first, by the 

 means which are represented in the accompanying 

 figure. 



Vulcanised india-rubber sheeting being at once elastic 



and dielectric, it occurred to me that this material was 

 the very thing for putting to the test of experiment what I 

 believed might happen in the elastic and dielectric sheath 

 of muscular fibre. I therefore took a band of this sheet- 

 ing, provided it with the conducting surfaces necessary 

 for charging and discharging it as a Leyden-jar is charged 

 and discharged, and had constructed an apparatus for 

 showing whether or not the anticipated changes in length 

 were produced by this charging and discharging. The 

 band (which is to be regarded as the counterpart of a strip 

 of the actual sheath of the muscular fibre) is 14 in. in 

 length by 2 in. in breadth, the commercial number of the 

 india-rubber sheeting being 30. The necessary conducting 

 surfaces to allow of the charging and discharging are made 

 by painting the band on each side with fluid dutch-metal, 

 care being taken to leave at the edges a sufficient un- 

 painted margin to secure the necessary insulation of the 

 two painted surfaces. The frame-work of the apparatus con- 

 sists of two strong brass pillars, iSin. in height, and 4 in. 

 apart, rising from a fiat brass stand. Across these pillars 

 work two axles, horizontal in direction and parallel to 

 each other — the one at the top, the other near the base, 

 immediately above the stand. At the middle of the upper 

 axle, midway between the pillars, is a wheel with a 

 grooved edge, 2 in. in diameter, which may be called the 

 driving-wheel ; at one end, which projects beyond the 

 pillar on that side, is another and larger wheel, 6 in. in 

 diameter, also with a grooved edge, which may be called 

 the multiplying-wheel. At one end of the lower axle, 

 beyond the pillar on that side and immediately under the 

 multiplying-wheel is a collar with a grooved edge ; at 

 the other end, also beyond the pillar on that side, is a 

 socket for carrying a long index, of which the free end 

 moves backwards or forwards before a graduated arc 

 fixed immediately over the socket upon the same pillar 

 near its top. The two axles move together, the upper 

 telling upon the lower by means of an endless band 

 which at one and the same time bites in the grooved edge 

 of the multiplying-wheel at the end of the one, and in 

 that of the collar at the end of the other ; and thus the 

 movements of the index before the graduated arc are 

 made to represent a very considerable exaggeration of the 

 movements of the upper axle. The india-rubber band is 

 clipped at each end in a clamp, acting by screws, and 

 having a hook on its free edge ; and, being so clipped, it 

 is fixed in a a vertical position by passing the hook on 

 the clamp at its lower end into a socket provided for it 

 on the stand, and by attaching the hook on the clamp at 

 its upper end to a string which passes over the grooved 

 edge of the driving-wheel to a short hanging rod with a 

 button at its lower end, upon which rod are to be slipped 

 coin-Uke weights, notched in the centre for this purpose, 

 which weights have to be so adjusted as to put the band 

 gently upon the stretch. In this way the band is so fixed 

 that it cannot lengthen or shorten without these changes 

 being made to tell upon the index, for as it lengthens 

 or shortens, the driving-wheel which moves the index 

 must be made to turn this way or that by the string 

 which bites into its grooved rim in passing from the 

 band to the weights. For charging and discharging, two 

 short pillars are fixed to the stand in front of and at a 

 short distance from the bottom of the band, that for the 

 foniier purpose having an ebonite shaft, that for the latter 

 being altogether metal ; and through holes in the caps of 

 these pillars the rods which are intended to serve as 

 the actual channels for the charge and discharge are 

 made to slide horizontally backwards or forwards in a 

 suitable direction. In charging, the electricity is supplied 

 to the metalhc surface on the front of the band by push- 

 ing forwards the charging rod so as to touch this surface, 

 and at the same timetakmg care that the discharging rod 

 is drawn back so as to leave the necessary break in the cir- 

 cuit. In discharging, the discharging rod is pushed home 

 so as to complete the circuit between the two opposite 



