Page:The Harveian Oration,1902.djvu/29

 Harvey, as we have seen, intended to discuss the subject in his "Medical Observations." The philosopher Malebranche is said to have propounded a vaso-motor theory of emotional expression according to which the flow of vital spirits to the brain and the organs was regulated by a special system of nerves. But Willis appears to have first actually demonstrated the nerves of the blood-vessels and to have indicated their true function; for he describes nerves from the cardiac and abdominal plexuses as accompanying the blood-vessels, which he graphically likens to twigs of ivy embracing and surrounding their trunks and branches. Of their function, in speaking of the solar plexus, he says:—

"That from this plexus many fibres and shoots going forth are inserted into the Trunk of the Aorta nigh its descending, and that these reaching towards the intestines accompany the Blood-carrying vessels, and in several places climb over them; from hence it may be inferred that nerves also in the Abdomen are like Bridles and Reins cast on the sanguiferous Vessels, which, either by straining or pulling them together, may