100 OF VITAL MOTION. 



A word, however, may be said upon the two agents 

 that especially concern muscular irritability, viz., 

 opium and strychnia. Now, we know very well that 

 a tetanic state is very apt to happen in frogs that are 

 poisoned by these drugs, and the question is as to the 

 cause of these spasms. Are they stimulated ? Against 

 this view it may be said that opium produces direct 

 depression of all the vital faculties, of which depression 

 it is not unreasonable to suppose that the spasm may 

 be one of the signs. And in relation to strychnia, it 

 may be asked if it is not begging the question to say 

 that it acts by stimulating the nerves. If spasm is 

 the only proof, then all the previous arguments upon 

 muscular action are against the conclusion ; moreover, 

 there is undoubted evidence of the existence of severe 

 convulsive diseases in which there is no such irrita- 

 tion, and in which the system is torpid, and in every 

 respect the reverse of what is called excitable. 



The whole subject, however, is so obscure that we 

 must be content to wait the results of future investi- 

 gation. Meanwhile, however, we may contend that 

 there is at least an equal amount of reason for the 

 supposition that the muscular contraction, which is the 

 result of the operation of chemical agencies, is the sign 

 of a negation and not of a communication of force. 



We have now studied the phenomena of 

 muscular action in relation to every aspect of physical 



