570 THE OUTGO OF ENERGY 



about one millimetre posterior to the corpora 

 quadrigemina to a point about four millimetres 

 posterior to those bodies. 



The Vasomotor Functions of the Spinal Cord. 

 1. Divide the cord just posterior to the bulb. 

 (A fresh frog may be required. In that case, 

 remember to curarize.) 



The division of the fibres connecting the vaso- 

 constrictor centre with the cord will be followed 

 by the dilatation of the vessels in the web (i. e. 

 the flow will be more rapid). 



2. Stimulate the peripheral segment of the 

 divided cord. 



The blood-vessels will constrict. 



Thus the neuraxons (axis-cylinder processes) 

 of the bulbar vasomotor cells pass through the 

 spinal cord on the way to their respective blood- 

 vessels. 



It should now be determined whether these 

 fibres pass to the blood-vessels without interrup- 

 tion, or whether they end in contact with spinal 

 vasomotor cells through which the connection 

 with the blood-vessels is made. 



3. Wait five minutes and then note the flow 

 through the capillaries. 



The dilatation observed immediately after the 

 separation of the cord from the medulla has given 

 place to moderate constriction. The tonus of the 



