340 PRODUCTION OF ELECTRICITY BY ANIMA-LS. 



Animal Electricity. 



416. Almost all chemical changes are attended with some 

 alteration in the electric state of the bodies concerned ; and 

 when we consider the number and variety of these changes in 

 the living animal body, it is not surprising that disturbances 

 of its electric equilibrium should be continually occurring. 

 But these, when slight, can only be detected by very refined 

 means of observation ; and it is only when they become con- 

 siderable, that they attract notice. Some individuals exhibit 

 electric phenomena much more frequently and powerfully 

 than others ; and cases are occasionally recorded in the 

 Human subject, in which there has been a most decided pro- 

 duction of electricity, which manifested itself in sparks when- 

 ever the individual was insulated. 



417. The sparks and crackling noise, however, which are 

 occasionally observed on pulling off articles of dress that 

 have been worn next the skin, especially in dry weather, are 

 partly due to the friction of these materials with the surface and 

 with each other ; the production of electricity being greatly influ- 

 enced by their nature. Thus, if a black and a white silk stocking 

 be worn, one over the other, on the same leg, the manifesta- 

 tion of electricity when they are drawn off, especially after a 

 dry frosty day, is most decided ; but this would also be the 

 case if they were simply rubbed together, without any con- 

 nexion with the body. 



418. In most animals with a soft fur, sparks may be pro- 

 duced by rubbing it, especially in dry weather ; this is familiar 

 to most persons in the case of the domestic Cat. But the 

 electricity thus produced seems occasionally to accumulate in 

 the animal, as in the Ley den jar, so as to produce a shock. 

 If a cat be taken into the lap, in dry weather, and the left 

 hand be applied to the breast, whilst with the right the back 

 be stroked, at first only a few sparks are obtained from the 

 hair; but after continuing to stroke for some time, a smart 

 shock is received, which is often felt above the wrists of both 

 the arms. The animal evidently itself experiences the shock, 

 for it runs off with terror, and will seldom submit itself to 

 another experiment. 



419. But there are certain animals which are capable of 

 producing and accumulating electricity in large quantities, by 



