Page:The Harveian Oration,1902.djvu/33

 and greater excitability of the constrictors, but when special methods of stimulation are employed, the action of the vaso-dilators is made clearly manifest. All the organs supplied with vaso-constrictors are furnished also with vaso-dilators, but the proportion differs, and in some organs, such as the brain and lungs, it is still a question whether there are any vaso-motor nerves at all. In reference to the lungs, in which Bradford and Dean, as well as Francois Franck, claim to have demonstrated the existence of vaso-motor nerves, the recent experiments of Brodie and Dixon are of special importance and significance. They found that no change in the calibre of the pulmonary arterioles could be produced by direct stimulation of any of the fibres proceeding to, or emanating from, the stellate ganglion. Further, when the lungs were perfused with blood containing suprarenal extract, which, as has been shown by Schafer and Oliver, usually causes constriction of the