572 THE OUTGO OF ENERGY 



have passed into dilated smaller arteries and 

 veins. It would be found, on waiting, that this 

 effect is not a passing consequence of inhibition. 

 The destruction of the spinal cord has changed 

 the distribution of the blood. 



The Vasomotor Fibres leave the Cord in the 

 Anterior Roots of Spinal Nerves. 1. Remove 

 the arches of the 5th, 6th, 7th, 8th, and 9th ver- 

 tebrae and lay bare the cord, in a large frog in 

 which the motor nerves have been paralyzed with 

 curare. Note the capillary flow in the web. On 

 the side on which the web- vessels are examined, 

 tie a silk thread around each of the anterior roots 

 near their origin from the cord, and sever the roots 

 between the ligature and the cord. 



The vessels will dilate. 



2. Stimulate the peripheral ends of several of 

 the divided roots. 



Constriction will follow. 



The vascular dilatation which follows the de- 

 struction of the spinal cord is not permanent. 

 After a time the vessels regain their tonus. It is 

 probable, therefore, that vasomotor nerve cells 

 exist outside the spinal cord, and this conclusion 

 is confirmed by the results gained on warm-blooded 

 animals with the nicotine method. Langley has 

 found that the injection of about ten milligrams 

 of nicotine into a vein of a cat will prevent, for a 



