Page:The Harveian Oration,1902.djvu/53

 vaso-constriction. The stronger the stimulus the greater the effect, and for this reason, perhaps, the more painful feelings and emotions, which can be more readily experimentally-induced, cause more marked vaso-constriction than those that are more agreeable. The heart is accelerated, the respiratory rhythm is altered, becoming more rapid and more profound, with obliteration of the respiratory pause, and at the same time there is a general rise of blood pressure. If the volume of the brain is simultaneously registered by the plethysmograph, as Mosso has described, and Brodie and I have verified, one observes almost constantly an increase. This seems to indicate that there is a relation of antagonism between the volume of the brain and that of the extremities. But this is not an absolute rule, for Mosso has observed that the oscillations in the brain volume do not in all respects run parallel to those of the extremities, probably owing to local variations in the cerebral blood-vessels themselves. Whether the quality of the sensation or emotion as such—i.e., whether it be agreeable or disagreeable, pleasurable or pain-