Page:The Harveian Oration,1902.djvu/26

 arise along which the pain is referred, he has succeeded in mapping out with marvellous definition the segmental relations of the sensory nerves of the various viscera. From these it appears that painful conditions of the heart refer not only into the regions connected with the vagi, but also into those of the upper dorsal segments whence the heart also receives its chief motor supply. The sensory nerves of the heart, therefore, lie not only in the vagus, but also in the rami communicantes of the upper dorsal nerves. What is the respective origin of these nerves in the heart is not as yet certain, but the recent investigations of Koster indicate that the depressor nerve, the afferent nerve of the heart, par excellence, is in reality the sensory nerve of the aorta and not of the heart itself. The centres, both of the cardiac inhibitors and accelerators and augmentors are situated in the medulla oblongata—not in the cerebellum, as Willis supposed—the former in the vagal nucleus, where a pin-prick will arrest the heart, the latter in a point not yet accurately determined.