232 SPECIAL PHYSIOLOGY. 



those muscles to contract, by galvanizing their motor nerves at such 

 a distance from them, and in such a manner, that no part of the 

 exciting electrical current can directly reach those muscles. When 

 this is done, the muscles contract, and, as we already know, this is 

 accompanied by disturbances, i. e., by intermittent diminutions in their 

 normal current; and hence, in consequence of these variations, they 

 excite the nerve of the rheoscopic limb, which is resting upon them, 

 and this, in turn, causes contractions in the muscles of that limb. 

 Here, then, is an example of a nerve excited, so as to cause contrac- 

 tions of its muscles, by the agency of electrical currents occurring in 

 a living tissue, viz., in the muscles of another frog's leg. To succeed 

 in this experiment, it is necessary that the nerve of the rheoscopic 

 limb be placed, not merely across the contracting muscles, but oblique- 

 ly or longitudinally for some little distance upon them. A very 

 powerful exciting battery may be made, by placing a chain of skinned 

 frog's legs one upon another. 



Dr. Radcliffe, whose opinion on the passive nature of muscular con- 

 traction has been elsewhere mentioned, supposes that the electromotive 

 condition of the nervous molecules, is not dependent on the existence 

 within them, of current electricity, or continuous internal currents, 

 but rather upon a static form of electricity. The current established 

 through the galvanometer, by a portion of nerve, he believes to be 

 only an induced current; and, to explain it, he supposes that nerves, 

 or their nerve fibres, consist of two sets of electrical molecules an 

 external or superficial set, having their surfaces positive, and a central 

 or axial set, having their surfaces negative. He further believes that 

 the diminution or cessation of the obvious nerve current, when a mus- 

 cle is in action, justifies the supposition that muscular contraction 

 may depend, not on a direct stimulation of its fibres by the nerve 

 current, or on a disturbance of the muscular current, but on the sus- 

 pension or absence of the static currents, which are present in inactive, 

 but living, nerve and muscle. The relaxed state of the muscle, he 

 believes to be maintained by the presence of the static current. The 

 rigor mortis, he likewise supposes to depend on a similar cessation of 

 these currents. He also explains the electrotonic phenomena of ex- 

 cited nerves, in accordance with his peculiar views. 



Nerve Force. 



The phenomena which take place in nerve fibres and nerve cells, 

 when excited to action by any stimulus, have led to the supposition 

 that there is manifested within them at such times, a peculiar force, 

 which is called the nerve force, or vis nervosa, just as the electric and 

 magnetic phenomena produced in electric or galvanic, and magnetic 

 apparatus, are supposed to be the result of an electrical and magnetic 

 force, called either electricity or magnetism. Three different views 

 are entertained respecting the nature of this nerve force. By some, it 

 is regarded as a special force, proper to living nerve substance, a vital 

 force wholly different, even in kind, to any other force in nature. By 

 others, it has been considered to be the same as electricity, or a mere 



