Jan. 4, 1872] 



NATURE 



187 



suggested to the mind by the way in which the needle 

 swings back past zero when the state of action is first 

 set up, is at once corrected by the position which the 

 needle takes up a moment or two later, and also by the 

 fact that when the muscle-current of the (On/nuii-ti 

 muscle is admitted into the coil of the galvanometer while 

 the needle is resting at zero — when, that is, the experiment 

 is not complicated by the muscle-current of the relaxed 

 muscle being in the coil when the state of contraction is 

 set up in the muscle — the needle is found to move in the 

 same direction as that in which it moved under the current 

 of the re/a.xrd muscle, but not to the same distance from 

 zero by a very great deal. So that, in fact, this " negative 

 variation" of the muscle-current is nothing more than a 

 sudden disappearance or failure of this current, and no 

 good is gained by retaining a name which only serves to 

 confuse and perplex. 



Substituting the new quadrant electrometer of Sir 

 William Thomson for the galvanometer, tensional changes 

 are detected which are in every way parallel with the cur- 

 rent changes which have been mentioned. 



With this instrument, it is found that the surface made 

 up of the sides of the fibres in living muscle, and that 

 made up of either one of the two ends of these fibres, are 

 in opposite electrical conditions, the ray of light marking 

 the movement of the aluminium needle passing in the 

 direction indicating positive electricity under the charge 

 supplied by the former surface, and in the direction indi- 

 cating negative electricity under the charge supplied by 

 the latter surface — passing, that is to say, not in one 

 direction only, as it would do if the needle were acted 

 upon by charges differing, not in kind, but in degree only, 

 but to the right in the one case and to the left in the other. 

 It is found, indeed, not only that the surface made up 

 (if the sides of the fibres of living muscle is positive, and 

 that made up of eitherendof these fibres negative ; but also 

 that the former surface is more positive and the latter 

 more negative as the distance increases from the line of 

 junction between these surfaces. With this instrument, 

 too, it is found that these indications of free electricity 

 fail pari passu with this failure of the " irritability " of 

 the muscle, that they have disappeared altogether before 

 the advent of rigor mortis, and also that there is a change 

 which serves to point to discharge, more or less com- 

 plete, when muscle passes from the state of rest into that 

 of action. Thus — in illustration of this latter fact — if the 

 ray of light on the scale stand at 30' under the charge 

 supplied to the electrometer by either one of the two 

 surfaces of living muscle during the state of rest, it will 

 stand at 5' only, or still nearer to zero, under the charge 

 supplied by the same surface during the state of action. 

 The dift'erence is always marked, and always of the same 

 character ; and, being so, the proof of discharge during 

 action would seem to be as complete as may be, seeing 

 that the instrument only takes cognizance of electrical 

 changes of the nature of charge and discharge. 



These, then, are the facts which may be looked upon 

 as fundamental. There are the facts brought to light by 

 Du Bois-Reymond through the instrumentality of the gal- 

 vanometer — the muscle-current, present in living muscle 

 during the state of rest, suddenly disappearing when the 

 state of rest changes for that of action, gradually disap- 

 pearing as muscle loses its " irritability," and absent 

 altogether in rigor mortis ; there are the facts which I 

 myself have been able to make out for the first time by 

 means of the wonderfully sensitive new quadrant electro- 

 meter of Sir William Thomson — the two opposite 

 charges of electricity, one positive, the other negative, 

 present in living muscle during the state of rest, disap- 

 pearing suddenly when this state changes for that of 

 action, gradually disappearing before, and altogether 

 absent in, rigor mortis. And this is all that need be said 

 upon this subject at present. 



And as in muscular so in nerve tissue, there is the 



current, in this case called the nerve-current, and there 

 are the two opposite charges, positive and negative, this 

 current and these charges being present during life, dis- 

 appearing suddenly when the state of rest changes for 

 that of action, disappearing 'gvnAnvWy pari passu with the 

 " irritability," and absent altogether at the time when rigor 

 mortis has seized upon the muscles ; and in truth every 

 particular in the electrical history of the muscle is re- 

 peated with strict exactness in the electrical history of 

 the nerve. 



In these two tissues, muscle and nerve, there is no 

 difficulty in arriving at a knowledge of these facts ; in 

 other tissues the case is difterent. In other tissues, 

 indeed, all that can be said is that faint indications of 

 electricity are to be detected during life only, and that in 

 some of the fibrous structures there are differences between 

 the surface made up of the sides of the fibres and that 

 made up by either one of the two ends, which correspond 

 to those met with in muscle and nerve. 



These then being the fundamental points in the history 

 of animal electricity, the question is as to their meaning. 

 To what theory do they point ? 



In order to account for this muscle-current and nerve- 

 current. Dr. Du Bois-Reymond supposes that the muscle- 

 fibre and nerve-fibre (the same law applies absolutely to 

 both) are made up of what he calls peripolar molecules — 

 of molecules, that is to say, which are (with the exception 

 of certain moments in which these electric relations may 

 be reversed) negative at the two poles and positive in the 

 equatorial belt between those poles. He supposes that 

 the sides of the fibres are positive because the positive 

 equatorial belts are turned in this direction, and that the 

 two ends are negative because the negative poles of the 

 molecules face towards the ends. He supposes also that 

 the muscle-current and nerve-current are merely the out- 

 flowings of infinitely stronger currents ever circulating in 

 closed circuits around the peripolar molecules of the 

 muscle and nerve respectively. And this view no doubt 

 has much to recommend it. 



But another view may be taken of this matter — a view 

 according to which this electrical condition of living 

 muscle and nerve during rest is, not current, but static ; 

 and this view is that which recommends itself to my 

 mind as in every way more simple, more comprehensive, 

 and more to the point practically. 



In taking this view the great resistance of the animal 

 tissues to electrical conduction serves as the starting point. 

 I assume that parts of these tissues may be bad enough 

 conductors to allow them to act as dielectrics. I assume 

 that the parts which are thus capable of acting as dielec- 

 trics are the sheaths of the fibres in muscle and nerve, 

 or the cell-membrane of the contractile cells of those fibres 

 in muscle which have no proper sheath. I assume that 

 a charge, usually the negative, may originate in the mole- 

 cular reactions of the contents of the sheath or cell-mem- 

 brane, and that this charge, acting upon the inner surface 

 of the sheath or cell- membrane, may induce the opposite 

 charge upon the outer surface of the sheath or cell- 

 membrane, and that in this way the sheath or cell mem- 

 brane during rest is virtually a charged Leyden-jar. 1 

 assume that this charge is discharged when the state of 

 rest changes for that of action. I assume that the sur- 

 face midc up of the sides of the fibres in muscle and 

 nerve is positive because positive electricity has bsen 

 /«(/«("<•(?' upon this surface, and that the surface made up 

 of either cut-end of the fibre is negative, because the 

 negative electricity, developed upon the inner surface of 

 the sheath or cell-membrane, is conducted to these ends 

 by the contents of the sheath or cell. 



All that I assume, indeed, may be readily illustrated 

 upon a small cylinder of wood, left bare at its two ends, 

 and having its sides covered with a coating which may be 

 charged as a Leyden-jar is charged — a threefold coating, 

 formed of an inner and outer layer of tinfoil, with an in- 



