446 STIMULANTS TO CONTRACTION OF MUSCLES. 
it has been removed from the body, when it neither receives 
nor propels blood.1 In the same manner, the peristaltic 
motions of the intestine continue to propel its contents for 
some time after the general death of the body; and may even 
take place when the whole tube has been removed from it, 
and has been completely emptied. There is strong reason, in 
fact, for attributing to certain kinds of muscular tissue an 
inherent motility, in virtue of which it moves of ttself without 
any external stimulation ; the changes which are concerned 
in its nutrition developing a force which must manifest itself 
in action ; just as a Leyden jar, which is receiving a con- 
tinuous charge from an electrical-machine, discharges itself 
whenever its electricity attains a certain tension. 
582. But the muscles of the trunk, limbs, &c., are not 
called into action in this manner; for, as just now stated, 
a stimulus applied to any one part of these does not excite 
contraction in the whole muscle (as it does in the case of the 
heart), but only in the individual bundle of fibres irritated. 
These muscles are all of them supplied with nerves ($ 63) 
from the Cerebro-spinal system, or the nervous centres that 
correspond to them in Invertebrated animals ; and it is only 
by a stimulus transmitted to them along these trunks, that all 
the bundles of which the muscle is composed can be called 
into action at once. 
583. When the trunk of a nerve supplying a muscle is 
irritated by pricking, pinching, &c., in the body of a living 
animal, or in one recently dead, the whole muscle is thrown 
into contraction; and this contraction is peculiarly. strong 
when a current of Electricity is transmitted along the nerve. 
In cold-blooded animals, whose muscular fibre retains its vital 
properties for a much longer time after death than that of 
warm-blooded, this contraction may be excited by a very feeble 
current of electricity, even in a limb which has been separated 
from the body for twenty-four hours or more; and it was 
owing, in fact, to this circumstance, that the peculiar form of 
electricity which is now termed Galvanic or Voltaic was dis- 
covered. The wife of Galvani, who was Professor of Medicine — 
1 There is an instance on record, in which the heart of a st eon 
that had been removed from the body and had been inflated wit 
continued to beat until the auricle had become so dry as to rustle 
during its movements. 
