THE NEURO-MUSCULAR JUNCTION 279 



by section of the post-ganglionic sympathetic nerve-trunks. Its action 

 therefore must lie at the junction between nerve and muscle, and must be on 

 some intermediate or receptor substance developed at the myoneural junc- 

 tion, and having for its function the transference of the excitatory process 

 from the nerve fibre to the contractile substance of the muscle fibre. Similar 

 receptor substances may act as intermediaries in every case of propagation of 

 an impulse across a synapse of whatever description, and may by their pro- 

 perties determine the peculiar qualities of the synapse. We may compare 

 them to the fulminating cap which in a shell is used to transfer the process of 

 combustion from the slow-match to the bursting charge. Their existence is of 

 especial importance when we endeavour to investigate the mode of action of 

 drugs. It is probable that they will be found to play a great part in deter- 

 mining the differential action of drugs on various tissues in the body. 



