176 PRINCIPLES OF PHYSIOLOGY 



Edinburgh was in the daily habit of receiving 

 such a message ; it would not matter to him 

 if one day the message was transmitted to 

 him from a station half way between Edin- 

 burgh and Glasgow ; he would still believe it 

 came from Glasgow and he would, if necessary, 

 reply to that city. 



98. It is convenient, in the next place, to 

 consider the end-organs. These are highly 

 specialized organs found at the ends of 

 centrifugal nerves, and at the beginnings of 

 centripetal nerves. The endings of motor 

 fibres in muscular tissue are an example of the 

 first, and the structures in the skin connected 

 with the sense of touch represent the second. 

 End-organs are adapted to the stimulation 

 of certain tissues by the nervous impulse 

 coming from a centre or to the awakening 

 of a nervous impulse by stimuli acting on 

 the end-organ. Thus we have end-organs 

 in muscle at the termination of motor 

 fibres ; nerve fibres can be traced into 

 actual contact with secretory cells and blood 

 vessels ; and, in electrical organs, into special- 

 ized structures constituting the electric tissue 



