THE CIRCULATION OF THE BLOOD 



presence of an accompanying fall in general blood-pressure. More often 

 the type of vascular reflex is that of dilatation followed by constriction 

 of the brain vessels. If there is an accompanying sharp rise in general 

 blood-pressure, then the reflex cerebral vascular dilatation is followed by 



nee. ur VES. 



3-a 

 | -a. 



u a) 



S^ 





irl'&iig'^ i 



vaso-constriction which takes place while the general blood-pressure is yet 

 high. Weber suggests that this local vaso-constrictor mechanism provides 

 an apparatus for the regulation and control of the cerebral congestion 

 that results from the rise of general blood-pressure due to the operation of 

 the general medullary vaso-motor center. 



