other substances at a distance from them.

In this case, it should seem that the electric matter discharged from
the animal system (by which it is probably more exhausted and fatigued
than by ordinary muscular motion) would never return to it, at least so
as to be capable of being made use of a second time, and yet if the
structure of these animals be such as that the electric matter shall
dart from one part of them only, while another part is left suddenly
deprived of it, it may make a circuit, as in the Leyden phial.

As to the _manner_ in which the electric matter makes a muscle contract,
I do not pretend to have any conjecture worth mentioning. I only imagine
that whatever can make the muscular fibres recede from one another
farther than the parts of which they consist, must have this effect.

Possibly, the _light_ which is said to proceed from some animals, as
from cats and wild beasts, when they are in pursuit of their prey in the
night, may not only arise, as it has hitherto been supposed to do, from
the friction of their hairs or bristles, &c. but that violent muscular
exertion may contribute to it. This may assist them occasionally to
catch their prey; as glow-worms, and other insects, are provided with a
constant light for that purpose, to the supply of which light their
nutriment may also contribute.

I would not even say that the light which is said to have proceeded from
some human bodies, of a particular temperament, and especially on some
extraordinary occasions, may not have been of the electrical kind, that
is, produced independently of friction, or with less friction than
would have produced it in other persons; as in those cases related by
Bartholin in his treatice _De luce animalium_. See particularly what he
says concerning Theodore king of the Goths, p. 54, concerning Gonzaga
duke of Mantua, p. 57, and Gothofred Antonius, p. 123: But I would not
have my readers suppose that I lay much stress upon stories no better
authenticated than these.

The electric matter in passing through non-conducting substances always
emits _light_. This light I have been sometimes inclined to suspect
might have been supplied from the substance through which it passes. But
I find that after the electric spark has diminished a quantity of air as
much as it possibly can, so that it has no more visible effect upon it,
the electric light in that air is not at all lessened. It is probable,
therefore, that electric light c