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 motiltiy, in virtue of which it moves of itself 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 sturgeon, 

 that had been removed from the body and had been inflated with air, 

 continued to beat until the auricle had become so dry as to rustle 

 during its movements. 



