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elusion is borne out by the history of the muscular movements which 

 are manifested in the coats of vessels and in the heart, while at the 

 same time this view is found to give the clue to the physical inter- 

 pretation of " capillary action," and of rhythm, whether this be in 

 the heart or elsewhere. 



It is shown, also, that the same conclusion is borne out by the 

 pathology of tremor, convulsion, and spasm, of those diseases, that 

 is to say, in which muscular contraction is in excess. Thus, (to 

 mention one argument out of many,) the state of circulation which 

 is invariably associated with tremor, convulsion, and spasm, is one 

 which necessarily implies the diminution of all accustomed stimu- 

 lation in the muscle, for it is a state which borders closely upon 

 syncope or asphyxia. 



And, lastly, it is shown that there is nothing in the phenomenon 

 of muscular contraction which need prevent it from being referred to 

 the operation of that common principle of attraction which belongs 

 to muscle in common with all matter, and thus the general conclusion 

 is that another barrier between the organic and inorganic world is 

 broken down, and that muscular contraction is an effect of the 

 universal law of gravitation. 



There are, however, sundry grave objections to this theory, and 

 one main object of the paper under consideration is to remove them. 

 Thus, for example, if muscle contracts when nervous influence is 

 withdrawn, how is it that it relaxes when the nerve is divided or 

 otherwise paralysed ? and if a muscle contracts for want of blood, 

 how is it that it relaxes in syncope, asphyxia, and death ? These 

 objections are grave, but not unsurmountable, as the following hints 

 at explanation will serve to show. 



It must be understood, then, that that state of polar action which 

 is present in a muscle during rest and absent during contraction, is 

 re-established immediately after contraction ; it must also be under- 

 stood that this state of polar action in the muscle is suspended 

 during ordinary muscular contraction by certain changes which take 

 place in the nervous centre, and that it has died out when contrac- 

 tion happens after death, as in rigor mortis ; and the rest is suffi- 

 ciently simple. 



It is quite in accordance with the theory, then, that a muscle 

 should contract when nervous influence is withdrawn, and that it 



