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should relax after the nerve is divided or otherwise paralysed. At 

 the moment when the continuity of the nerve is broken the muscle 

 contracts, because the influence of the nervous centre is cut off; 

 but this contraction cannot continue, because that state of polar 

 action which antagonizes contraction is immediately re-established 

 in the muscle, and in the portion of nerve connected with it. This 

 relaxation, moreover, must continue, if the paralysed muscle be left 

 to itself, so long as the muscle continues to be the seat of this polar 

 action. And, on the other hand, this contraction must return when 

 this action is suspended, or diminished, or extinguished, as indeed 

 it does ; thus the muscle contracts when the polar action is sud- 

 denly suspended by galvanism or by the touch of a needle; thus it 

 contracts after the paralysis has continued for some time, and when 

 the failure in the nutrition of the muscle has entailed a correspond- 

 ing failure in its polar action ; and thus it contracts in rigor mortis, 

 when all polar action is finally extinguished. 



It is also in accordance with theory that tremor, convulsion, and 

 spasm should be caused by want of blood, and that they should 

 cease when the circulation fails, as it fails in syncope, asphyxia, or 

 death. During tremor, convulsion, or spasm, the muscles are insuffi- 

 ciently supplied with nervous influence, because the deficient supply 

 t)f blood to the nervous centres involves a corresponding deficiency in 

 the degree of innervation ; but once let the circulation fail below a 

 certain point, and the whole case is altered. During tremor, con- 

 vulsion, and spasm, the supply of blood to the nervous centres is in- 

 sufficient to keep up the normal degree of innervation, but it is suffi- 

 cient to prevent the nerves from being paralysed, and hence the con- 

 tractions in the muscles, for the nerves being conductors, the failure 

 in the action of the nervous centres is propagated along them to the 

 muscles, and of this failure the contractions are the consequence. 

 But if the circulation fails below a certain point, the nerves are 

 paralysed for want of blood, and being paralysed, the failure of in- 

 nervation in the nervous centres, even though this be now complete, 

 does not entail a corresponding failure in the polar action of the 

 muscle, because the nerves are no longer conductors; and not 

 doing this, the polar action of the muscle, which is much more 

 vigorous than that of the nervous centre and nerve, and far less 

 dependent upon the supply of blood, is immediately re-established, 



