NATURE 



{Jan. 4, 1872 



tetmediate layer of giitta-percha sheeting, the latter layer 

 projecting a little towards the two ends of the cylinder, 

 so as to secure the necessary insulation of the inner and 

 outer metallic surfaces ; for by charging the inner la\ cr 

 of foil \\ith negative electricity, this cylinder, which 

 may be regarded as a model of a muscular fibre, is found 

 to be, not only positive at the sides and negative at the 

 two ends, but more positive at the sides and more nega- 

 tive at each end as the distance increases from the line 

 of junction between the sides and ends. With this model 

 thus charged, indeed, it is easy to imitate all the pheno- 

 mena of the nerve-current and muscle-current, provided 

 the electrodes of the galvanometer be applied in a suitable 

 manner, and the charge kept up. With this model thus 

 charged, it is also easy to imitate all the tensional pheno- 

 mena of nerve and muscle which are made known by the 

 electrometer. And thus the nerve-current and muscle- 

 current, instead of being out-fiowings of infinitely stronger 

 currents ever circulating around peripolarj molecules, 

 may be secondary phenomena only, the accidental result 

 of certain points of dissimilar electric tension upon the 

 surface of the fibres of muscle and nerve being brought 

 into relation by means of the galvanometer or the electro- 

 meter, as the case may be. 



In this view, I have assumed that certain parts of nerve 

 and muscle were sufficiently bad conductors to enable 

 thein to act as dielectrics, but 1 had not, it is easy to see, 

 the firmest ground for this assumption. It was certain 

 that these tissues were bad conductors ; it was not certain 

 that they were bad enough conductors for my purpose. 

 Here, then, was occasion for new work — for work which 

 must be done before I could hope to gain a secure foot- 

 ing for my theory ; and this, therefore, was the task I set 

 myself a few months ago, and about which I have now 

 to say something. 



In this work I have made use of a Wheatstone's Bridge 

 having on each side resistance coils of the value respec- 

 tively of 10, 100, and 1,000 B. A. units, of a set of re- 

 sistance coils capable of measuring up to i,oco,ooo of the 

 same units, and of a battery consisting of six medium- 

 sized Bunsens cells. With this apparatus I have 

 measured the resistance of muscle, tendon, yellow elastic 

 Ugament, brain, and spinal cord, the portion measured 

 in each case being a parallelogram an inch in length by 

 '^,\( of an inch in breadth, formed by making a slice 

 with a Valentin's knife, of which the blades were }y, of 

 an inch apart, and then cutting a strip from the slice by 

 moving the knife, with its blades still separated to the 

 same degree, at right angles to its surface.' In order to 

 eliminate the resistance due to secondary polarity, I 

 measured each of these bodies at '25, '50, and 75 of the 

 inch, as well as at the full inch, the fact being, as 

 was pointed out by Sir Charles Wlrcatstone in his first 

 great paper on the means of measuring electrical resist- 

 ance, that while the resistance of a conductor increases 

 with its length, the resistance due to secondary polarity 

 remains the same everywhere. Thus, at '25 it is im- 

 possible to say how much of the' resistance met with 

 belongs to the body itself, and how much to secondary 

 polarity ; but not so after "25, at '50, or 75, or I'o ; for 

 the resistance belonging to secondary polarity being the 

 same at '50, 75, and r, as at "25, it follows that by de- 

 ducting the resistance at '25 from the resistance at '50, 

 75, and I'O the difference at each of these points will re- 

 present the resistance of the body itself between "25 and 

 that particular point. 



Of these measurements those which I made last of all 

 will serve as well as any others for the text of what I have 

 now to say, and these are as follows : — 



Inch. B. A. unil^ 



Muscle (ox) at -25 =■ 17,000 



•50 = 27,000 

 75 = 36,000 

 ro = 46,000 



Tendon (ox) 



Yellow elastic ligament (ox) 



Brain (ox) 



Spinal rord (ox) 



I had made several measurements before these, corre- 

 sponding more or less closely with them in results, and I 

 was proceeding to make others, with a view to arrive at 

 some common mean of numbers, when I found that the 

 resistance went on continually altering, every moment be- 

 coming higher and higher, until in the end it was beyond 

 the reach of my means of measurement. 



Thus, in the strip of spinal cord, the resistance at '25 

 inch, which at first was 8,300, was 180,000 in five hours, 

 and more than 1,000,000 twelve hours later. 



Thus, the resistance of the strip of brain, which at first 

 was 1 1,500 at "25 inch, was 25,000 five hours later, and up- 

 wards of 1,000,000 after the still further lapse of a dozen 

 hours. 



And so, likewise, with muscle, and tendon, and yellow 

 elastic ligament, there was a corresponding increase of 

 resistance when the measurement was repeated at these 

 different times after the first trial. 



Nor was this the only proof of a change of this sort ; for 

 on repeating these measurements on the same specimens 

 some days later, after they had become thoroughly dried 

 up, I found that the very shortest length which could be 

 got for measurement — a length .so short, that the two 

 electrodes conveying the measuring current were all but 

 touching — gave a higher resistance than that which could 

 be gauged by the means at m.y disposal. 



These, then, being the facts, it was evidently useless to 

 go on searching for any numbers which could express 

 anything like a common mean of resistance. It was 

 evident, indeed, that the soft tissues, one and all, apart 

 from moisture, were to be looked upon as insulators, 

 rather than as conductors. Nay, it was possible that they 

 might be insulators rather than conductors even in the 

 fresh state ; for it is quite supposable that in this fresh 

 state the walls of the fibres and cells forming these tissues 

 may be virtually dry, with moisture on each side, not with 

 moisture percolating from side to side, and that the degree 

 of resistance presented by these tissues, when fresh, is 

 not that which would be encountered if the current passed 

 across these walls, but that which is encountered by the 

 current in passing along their outer moistened surface. 

 It is quite supposable that the measuring current may 

 not pass across the walls of the cells and fibres at all, 

 but may glide over and between them only. All this is 

 supposable ; and therefore, the facts being as they are, I 

 am, as I conceive, at liberty to assume that the walls of 

 fibres and cells are sufficiently non-conducting to justify 

 me in adopting the theory which I have ventured to pro- 

 pose — a theory, according to which, the electrical condition 

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

 — the sheath of the fibre, or membrane, taking its place, 

 being always charged as a Leyden-jar is charged, except 

 during the time of action, when there is a discharge of 

 this charge — a theory which, to say the least, has a less 



