Page:The Harveian Oration,1902.djvu/45

 holism dissolved in the lymph which bathes the cerebral arterioles—products capable of inducing variation in the calibre of the blood-vessels in correspondence with local variations in functional activity. This, however, has been contested by Hill. Brodie and I have, however, succeeded in rendering it more than probable that the cerebral blood-vessels are under the influence of vaso-motor nerves, though so far we have not been able to determine their origin and course.

As already mentioned, perfusion with supra-renal extract of an organ supplied with vaso-motor nerves causes constriction of the arterioles so that the flow through the capillaries is diminished or altogether stopped. It was found by Biedl and Reiner that injection of suprarenal extract into the cerebral end of the carotid caused a rise of blood pressure in the circle of Willis, and diminution of the outflow from one of the lateral sinuses—a result which might be attributed to the action of adrenalin on the terminals of cerebral vaso-motor nerves. But the conclusion is not free from fallacy owing to the non-determination of the condi-