NERVOUS CONTROL OF THE BLOODVESSELS. 317 



flow of blood, or in other words, is associated with a vaso-dilator 

 effect, probably dependent on the inhibitory effect of certain centri- 

 fugal fibres which control the local agencies. 



Thus we must suppose that there exist local agents under the 

 control of the medullary centres, and that there are two distinct 

 efferent and afferent sets of exciting and inhibitory fibres passing 

 between the centre and periphery, along two perfectly distinct 

 routes ; one being in the direct track of the ordinary functional 

 nerve of the part, the other being in the sympathetic, which to 

 a great extent runs along the vessels themselves, and forms most 

 intricate networks capable of carrying impulses in all imaginable 

 directions. 



