ELECTRICAL RELATIONS OF MUSCLE. 



815 



the animal with strychnia. In whatever mode the tetanized state is induced, 

 the same result follows, the needle of the galvanometer passes over to the 

 negative side. Ranke 1 has noticed the remarkable fact that dead muscle is 

 a better conductor of electricity than living, and that the conducting power 

 of muscle exhausted by exercise is also increased. This he attributes to the 

 accumulation of the products of disintegration, and especially to that of 

 lactic acid. Living muscle conducts electricity about three million times 

 worse than mercury, and fifteen million times worse than copper. 



666. The rapidity with which the mandates of the Will are communicated 

 to and executed by the Muscles is immeasurable; but Helmholtz has shown 

 that if an electric spark, whose duration does not exceed one gJo^ 1 or TOfltli 

 of a second, be allowed to strike a portion of fresh muscle, a measurable 

 period, amounting to T oo tn or Too tns f a second, intervenes before the com- 

 mencement of contraction. This he terms the period of latent contraction 

 or excitation. At the commencement of the contraction which succeeds, an 

 instantaneous electrical discharge occurs, lasting less than the joVc^ f a 

 second, and comparatively weak, but still probably equivalent to that of the 

 electric organ in fishes. 2 The contraction which then takes place is not 

 sudden and complete, but is divisible, according to Kliinder, 3 into four stages, 

 in the first of which the movement of contraction commences and slowly 

 increases ; iu the second there is great increase in the rapidity of the con- 

 traction ; the third is the period of maximum rapidity, and in the fourth 

 there is a diminution of the rapidity. The first period can be much pro- 

 tracted by heavy weighting, and the last period is very variable. Kltiuder 



Diagram of a muscle curve as drawn on a travelling surface, c, the Hue described by the point of 

 the lever connected with the muscle ; a, the line described by marking lever; 6, the line described by 

 the tuning-fork. The vertical line, ?., marks the moment of stimulation ; TO', the beginning, m s , the 

 maximum, and m?, the end of the contraction of the muscle. 



gives as the duration of the latent excitation of fresh and lively muscle 

 jfo-ths of a second, but when exhausted and heavily weighted it rises to 

 T nsth of a second ; previous extension of the muscle diminishes the duration 

 of the latent excitation, as Helmholtz also found.* The true curve of con- 



1 Tetanus, Leipzig, 1865. 



2 See Donders's Essay on the Constituents of Food, translated by Dr. Moore, Dub- 

 lin, 1866, p 14, where it is quoted as the observation of Meissner, and as corrobo- 

 rated by v. Bezold. 



3 Op. cit., p. 129. 



4 Kanvier (Comptes Rendus, Ixxvii, p. 1105, and Archiv. de Physiolog., t. vi, p. 1) 



