552 EVOLUTION OF HEAT, LIGHT, AND ELECTRICITY. 



inond, upon the relative electrical states of different parts of muscles and 

 nerves. If the two extremities of a Muscle, removed from the body of an 

 animal very recently killed, be applied to the two electrodes of a delicate 

 galvanometer, there is usually some deflection of the needle; this being 

 greater, in proportion to the difference in the arrangement of the muscular 

 and tendinous elements at the two extremities. Although the direction of 

 the current is constant for each muscle, yet there is no constant relation be- 

 tween the direction of the currents and the position of the muscles in the 

 body ; thus in the gastrocnemius of the Frog's leg, the direction is from the 

 foot towards the body, whilst in the sartorius it is the reverse. Taking all 

 the muscles of a part together, however, there is usually such a want of bal- 

 ance between the opposite currents, that a constant current is established in 

 the direction of the strongest and most numerous of the separate muscular 

 currents; this, in the Frog, passes uniformly from the hind feet towards the 

 head, and was at one time supposed to be peculiar to that animal ; but a 

 similar current may almost always be detected in other animals. The mus- 

 cular current grows feebler and feebler, the longer the muscle has been re- 

 moved from the body ; it is affected by any agents which tend to lower its 

 vitality, and becomes extinct as soon as its contractility ceases. From the 

 experiments of M. Du Bois-Reymond, it may be concluded that the current 

 in the arm of Man, when at rest, is from the shoulder towards the points of 

 the fingers. (The special conditions of the "Nervous" and "Muscular" 

 currents will be hereafter fully considered in the chapters devoted to the 

 Nerves and Muscles respectively.) 



443. Some of the most important parts of the body being thus in a state 

 of constant disequilibrium with regard to each other, it is not surprising that 

 the Electric state of the whole should be ordinarily in disequilibrium with 

 that of surrounding bodies. This difference, however, is usually prevented 

 from manifesting itself, in consequence of the restoration of the equilibrium 

 by the free contact which is continually taking place between them ; and it 

 is for the most part only when the Human body is insulated, that it becomes 

 apparent. The galvanometer is then affected, however, by the contact of 

 one of its electrodes with the person insulated, and the other with any neigh- 

 boring uninsulated body; and also by the contact of the electrodes with the 

 hands of two persons both insulated, who join their other hands together, a 

 difference in the electrical states of the two individuals being thus indicated. 

 The electricity of Man is most commonly positive, and irritable men of san- 

 guine temperament have more free electricity than those of phlegmatic char- 

 acter. The electricity of women is more frequently negative than that of 

 men. There are persons who scarcely ever pull off articles of dress which 

 have been worn next the skin, without sparks and a crackling noise being 

 produced ; especially in dry weather, when the electricity of the body is re- 

 tained, instead of being rapidly dissipated as it is by a damp atmosphere. 

 The effect is usually heightened, if silk stockings and other silken articles 

 have been worn, since these act as insulators. It is doubtless in part attribu- 

 table to the friction of the articles of dress against each other and against 

 the body ; but w r e can scarcely doubt that it is partly due to the generation 

 of electricity in the body itself, since it bears no constant relation to the 

 former of these supposed causes. Thus a Capuchin friar is mentioned by 

 Dr. Schneider, 1 who, on removing his cowl, always found a number of shin- 

 ing crackling sparks to pass from his scalp ; and this phenomenon continued 

 still perceptible after a three weeks' illness. The most remarkable case of 

 the generation of Electricity in the Human subject at present known, was 



1 Caper's Wochenschrift, 1849, No. 15. 



