340 
PRODUCTION OP ELECTRICITY BY ANIMALS. 
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 he continually occurring. 
But these, when slight, can only be detected by very refined 
means of observation ; and it is only when they become com 
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 Leyden 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 
