April 17, 1879J 



NATURE 



563 



was in the first place necessary to determine whether absolutely 

 uninjured muscles are the seat of a muscuhu: current. 



Muscles cut out of the body possess almost invariably imper- 

 ceptible injuries of a mechanical or chemical nature. In the 

 first researches of du Bois-Reymond the muscles were reg^arly 

 moistened with saturated solutions of common salt, and thereby, 

 to a certain extent, corroded. Hence he was led to ascribe to the 

 natural terminations of muscular fibres the negative potential 

 which is exhibited by artificial transverse sections. This source 

 of error was indeed discovered by du Bois-Reymond himself ; 

 but, after he had removed it, there yet remained other electrical 

 phenomena apparently dependent upon the terminations of the 

 fibres, differing, however, entirely from that just mentioned and 

 obeying no strict rule in respect of direction of current. For 

 these phenomena the hypothesis of the parelectronomic layer 

 was introduced. 



The more, however, all injuries are avoided in the prepara- 

 tion of mascles about to be used for such observations, the 

 nearer is the approach to complete absence of currents. Chief 

 among the injuries in the case of the frog is that produced by 

 contact with the caustic secretion of the external skin,^ The 

 gastrocnemius is a muscle which may very readily be defended 

 firom such contact during its preparation, and it then exhibits 

 merely weak currents of indefinite direction, such as are found 

 in all circuits containing moist conductors.^ The muscles of the 

 thigh are, without exception, so connected with one another or 

 with neighbouring parts (skin, bones, &c,) that they cannot be 

 prepared without sustaining mechanical injuries in the course of 

 the necessary manipulation.* 



The statement that cold favours the development of a current- 

 less condition, or of opposing currents, in muscle is not confirmed. 

 The gastrocnemii of freshly-caught frogs do not differ electrically 

 from those of frogs kept for a long time previously in an ice- 

 cellar.* It is perhaps as well to observe that muscles which 

 have been actually frozen suffer injury in the subsequent process 

 of thawing, and are therefore to be avoided in these researches. 



The most promising method of testing perfectly uninjured 

 muscles appeared to be to examine them in the unskinned animal. 

 Du Bois-Reymond, 5 who was the first to hit upon this method 

 of observation, encountered an unexpected difficulty in the 

 cutaneous currents which almost all animals possess. If it is first 

 attempted to abolish the cutaneous currents by cauterising the 

 skin with salt solutions, the solution rapidly penetrates the skin 

 and attacks the underlying muscles ; this is observed to occur by 

 the gradual development of the same current as is induced when 

 the naked muscle is moistened by caustic agents. That the 

 muscles have already been attacked by the time the mus- 

 cular current is developed® may be directly shown by em- 

 ploying silver-nitrate as the cauterising sohition, when its 

 action upon the tissues subjacent to the skin is manifested by 

 rendering them opalescent.^ If the skin is cauterised in places 

 beneath which there are no aponeurotic muscular surfaces, no 

 muscular current can be discovered, or at the most only such 

 weak and irregular currents as count for nothing in the case of a 

 circuit formed of moist conductors ; not even the action of 

 caustics, nor abrasion renders the skin absolutely currentless.^ 



Fishes possess no cutaneous ciurent ; in their case it suffices to 

 connect any two points on the surface of the skin with the 

 galvanometer in order to ascertain the absence of a muscular 

 current.^ These animals, like the frogs used in these experiments, 

 must be rendered motionless by the action of curare. 



According to the recent researches of Engelmann the heart 

 offers an example in which it is easy to demonstrate the absence 

 of a muscular current, i** To do so it is merely necessary to 

 remove the pericardium, an operation which can be performed 

 without inflicting any injury upon the muscular substance. The 

 heart is currentless, but every injured spot in it possesses a 

 negative electric potential in reference to the rest. The pre- 

 existence theory can only explain this fact, and the previously 

 mentioned fact of the want of a current in the fish, by the most 

 improbable surmise made expressly to suit the cases, that no 

 muscular fibre has its termination directed towards the surface. 



' " Arch. f. d. ges. Physiol.," iii. p. 37, 1870. 



\ ^''v,^- '^' 35- 3 Ibid., XV. p. 227, 1877. 4 Ibid., XV. p. 226, 1877. 



5 Du Bois-Reymond, " Untersuchungen uber thier. Electr.," il 2 Abth 

 p. 7. 



* " Untersuchungen," Heft iii. p. 6, 1868. 7 Ibid., p. 14. 



8 Ibid., p. 14; "Arch. f. d. ges. PhysioL," iii. pp. 16, 25, 26, et sea. : iv. 

 p. 149. 1871. 



10 "■^'^^- f- d. ges. Physiol.," iv. p. 152, 1S7T. 



Engelmann, " Utr«cht'sche physiol. Oaderzoek." (3), iii. p. 82, 1874. 



2V0 Electromotive Force pre- existent in Muscle 



Another method of deciding whether a current pre-exists in 

 muscle appeared to be to determine whether, immediately after a 

 transverse section is made, the current is present in full force, or 

 whether an interval, however short, is required for the develop- 

 ment of it Were the latter the case it would be impossible for 

 the doctrine to be correct which assumes that electromotive 

 molecules exist ready formed in muscle and are merely laid 

 bare by the knife. The experiments, ^ which were made by 

 me in the years 1875 to 1877, to decide this question, have 

 settled it in opposition to the pre-existence theory. With the 

 help of a special apparatus the galvanometer circuit was closed 

 at the moment when an injury was inflicted upon a previously 

 uninjured muscle and then opened again after a very minute 

 interval of time. The deviation observed was smaller than in a 

 second trial made after the muscular current had already beeri 

 developed, and in which the current was allowed to act on the 

 galvanometer for the same period of time. The muscular cur- 

 rent, therefore, requires time for its development : it does not 

 pre-exist. 



Tfu Currents 0/ Nerves, of Glands containing Blood, of * 

 Plants, Q^'c. 



It was to be surmised that other protoplasmic tissues than 

 muscle would exhibit the phenomenon that portions of the tissue 

 which are in process of dying have a lower potential than 

 the yet living parts. First in importance in this respect is 

 nerve : the current of nerve was discovered by du Bois-RejTaond, 

 and, like that of muscle, explained by a molecular hypothesis. 

 Uninjxured terminations of nerves are, for many reasons, not 

 available for electrical researches ; 'nevertheless, on the ground 

 of the analogy to muscles, no one doubted the existence of a 

 current in nerves, nor the applicability to them of the molecular 

 scheme. With the discovery of the absence of a current in 

 uninjured muscles, however, the analogy cuts the other way.* 

 Henceforward there was not the slightest ground to assume the 

 existence of a current in ners'es at rest, except that developed 

 by artificial sections. We shall see that even the phenomena of 

 clectrotonus do not in the least justify the molecular hypothesis. 



Besides nerves, two other groups of protoplasmic apparatus 

 have been examined by myself ; and it has been found that in 

 them, also, artificial sections possess a negative potential when 

 compared mth the rest of the organs. In the cases of both 

 groups it afterwards appeared that the observations had pre- 

 viously been made by others. The first case was that of the 

 glandular oi^ans of the frog,^ in which Matteucci had already 

 found artificial cross- sections to be negative. I made out that this 

 character is only present when the vessels contain uncoagulated 

 blood, to the changes in which at the exposed surface it seems the 

 electromotive force is due. The second case was that of the 

 negative potential of artificial cuts and of cauterised spots in 

 plants,* facts first observed by H. Buff.* Both phenomena are 

 of such a kind that it is absolutely inconceivable to apply a 

 molecular theory to them ; yet notwithstanding the attempt has 

 been seriously made. 



The Dependence of Oirrents upon the Contact of Normal and 

 Injured Protoplasmic Tissue 

 ^Vhen examining the artificial cross-sections of plants I ob- 

 served that the lower potential of the exposed surface quickly 

 disappeared, but that a new section soon restored the original 

 condition. I explained this behaviour by supposing that, ac- 

 cording to the fundamental law, the lower potential of the 

 cross-section only persists so long as the cells which are impli- 

 cated in the section possess a remnant of living protoplasm. If 

 the cells are entirely dead, the ciurent must cease. In this 

 manner we can explain why, in plants with obviously long 

 fibres, artificial longitudinal sections have a higher potential than 

 artificial transverse sections ; ® for the cells which are split up 

 lengthwise die much more rapidly than those which are cut 

 across. The same transitory character of the current which I 

 have discovered in artificial cross- sections through vegetable 

 tissues has lately been observed by Engelmann '' in the case of 

 the heart and of organs possessed of unstriped muscular fibres, 

 and has been similarly explained. These organs are composed 



' "Arch. f. d. ges. Physiol.,' xv., p. 191, 1877. 



* " Untersuchungen," Heft iii., p. 25, 1868. 3 Ibid., p. 88. 



* "Arch. f. d. ges. Physiol.," iv. p. 155, 1871. 



5 Buff, " Ann. d. Chcmie," Ixxxix. p. 76, 1854. 



6 "Arch. f. d. ges. Physiol.," iv. pp. 159, 163, 1871. 



7 Engelmann, "Arch. f. d. ges. Physiol.," xv. p. 116, 1877. 



