EVOLUTION OF ELECTRICITY. 



635 



surface formed by cutting the muscle across (or artificial transverse section) is 

 placed against the other. When the two tendinous extremities of a muscle, 

 whose form is symmetrical or nearly so, are placed against the electrodes, the 

 deflection of the needle of the galvanometer is but slight; and the same is the 

 case with two transverse sections taken at equal distances from the two ends of 

 the muscle, and also with two points of the longitudinal section which are equally 

 distant from the middle of its length. But if the two points of the longitudinal 

 section applied to the electrodes be not equally distant from the centre of the 

 muscle, then the point which is nearest to the centre is positive to the one 

 which is nearest to the end ; and, in like manner, when the different parts of 

 the transverse section are tested in regard to each other, the points lying nearest 

 the surface of the muscle are found to be positive to those nearer its interior. 

 The intensity of the current, however, between any two points in the same 

 section whether transverse or longitudinal is always incomparably less than 

 that of the currents which are obtained between two points in different sections, 

 one in the longitudinal and the other in the transverse. These results may be 

 obtained, not merely with the entire muscle, but with insulated portions of it ; 

 and even, as we are assured by M. du Bois-Reymond, with a single primitive 

 fasciculus. Hence it. seems unquestionable that every integral particle of the 

 muscular substance must be a centre of electro-motor action, and must contain 

 within itself positive and negative elements ; and the variations both of intens- 

 ity and direction in the muscular current, under certain circumstances, are so 

 sudden and so extensive, that it appears impossible to account for them by any 

 change of larger heterogeneous elements, or in any other way than by assuming 

 corresponding changes of position in almost infinitely small centres of action. 

 It is indifferent what form is assigned to these electromotive molecules ; but it 

 would seem that they must have two negative polar zones, and a positive equa- 

 torial zone ; a combination of such elements being able to produce all the elec- 

 trical effects of a muscle in a state of rest. It seems altogether best to suit the 

 phenomena, to suppose that each of these peripolar molecules is formed by the 

 combination of two dipolar molecules, touching each other by their positive 

 poles as in the subjoined table, which represents a band of four series, A, B, C, 

 D, each series containing four dipolar molecules. 



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669. The current shown by the entire muscle, when made to form part of a 

 circuit, is only a derived current produced by incomparably more intense currents 

 circulating in the interior of the muscle around these ultimate particles, and 

 will vary greatly in intensity, according to the mode in which these particles 

 are arranged ; generally speaking, however, it increases both with the length 

 and with the thickness of the muscle. There is, however, another cause of a 



