210 Ay AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



any particular muscle or group of muscles causes a temporary increase in the 

 amount of blood which flows from the muscle vein. The stimulation of the 

 peripheral end of the nerve also increases the rate of flow through the muscle. 

 The same increase is seen on stimulation of the nerve when the muscle is kept 

 from contracting by curare, provided the drug is not used in amounts sufficient 

 to paralyze the vaso-dilator nerves. Mechanical stimulation by crimping the 

 peripheral end of the nerve gives also an increase. The existence of vaso- 

 dilator nerves to muscles must therefore be conceded. The presence of vaso-con- 

 strictor fibres is shown by the diminution in outflow from the left femoral vein 

 which followed Gaskell's stimulation of the peripheral end of the abdominal 

 sympathetic in a thoroughly curarized dog, but the supply of constrictor fibres 

 is comparatively small. In curarized animals reflex dilatation apparently follows 

 the stimulation of the nerves the excitation of which would have caused the 

 contraction of the muscles observed, had not the occurrence of actual contrac- 

 tion been prevented by the curare. The stimulation of the central end of 

 nerves not capable of calling forth reflex contractions in the muscles observed 

 — for example, the vagus — seems to cause constriction of the muscle- vessels. 



