VASCULAR REGULATION IN THE BRAIN 



243 



be at all times the same. But it was found that in animals bled to death 

 without any aperture being made in the cranium, the brain became pale and 

 anemic like other parts. And in death from strangling or drowning, there 

 was congestion of the cerebral vessels; while in death by prussic acid, the 

 quantity of blood in the cavity of the cranium was determined by the position 

 in which the animal was placed after death, the cerebral vessels being con- 

 gested when the animal was suspended with its head downward, and com- 

 paratively empty when the animal was kept suspended by the ears. Thus, 



FIG. 208. Showing the Origin and Course of the Vascular Vaso-motor Xerves for the Head. 



(Modified from Moret.) 



although the total volume of the contents of the cranium is probably nearly 

 always the same, yet the quantity of blood in it is liable to variation, its in- 

 crease or diminution being accompanied by a simultaneous diminution or 

 increase in the quantity of the cerebro-spinal fluid. The cerebro-spinal 

 fluid being readily removed from one part of the brain and spinal cord to 

 another, and capable of being rapidly absorbed and as readily effused, would 

 serve as a kind of supplemental fluid to the other contents of the cranium 

 to keep it uniformly filled. Although the arrangement of the blood vessels 

 insures to the brain an amount of blood which is tolerably uniform, yet with 



