574 THE OUTGO OF ENERGY 



corresponding spinal nerve, in which it continues 

 to its distribution. 



Vasoconstrictor Fibres in the Sciatic Nerve. 

 Curarize a frog sufficiently to paralyze the volun- 

 tary muscles (any excess of curare will paralyze 

 the vasomotor fibres also). Carefully destroy the 

 brain with the seeker, avoiding loss of blood. 

 Expose the right sciatic nerve for a 'short distance 

 on one side, using the greatest care not to injure 

 the blood-vessels. Tie a thread tightly around 

 the nerve near the upper end of the exposed por- 

 tion. Lay the frog, back upward, on the web-board, 

 placing the web of the right foot over the notch, 

 and securing it with fine pins. Examine the web 

 under a low power, to make sure that the circu- 

 lation has not been interrupted by stretching the 

 web. Place the secondary at such a distance 

 from the primary coil that the induced current 

 shall be barely perceptible to the tongue. Set 

 the hammer vibrating, and close the short-circuit- 

 ing key. Put the electrodes under the sciatic 

 nerve on the peripheral side of the ligature. Let 

 a second observer watch a small vessel of the web 

 through the microscope. Open the short-circuit- 

 ing key for a moment only. 



The blood-stream slows from constriction of 

 the supplying vessels, the contraction increasing 

 during a few seconds and then subsiding. 



