1889.] The Tnne.rvation of the Pulmonary Vessels. 369 



III. " The Innervation of the Pulmonary Vessels." By J. ROSE 

 BRADFORD, M.B., D.Sc., George Henry Lewes Student, and 

 H. PERCY DEAN, M.B., B.S., B.Sc. Communicated by E. A. 

 SCHAFER, F.R.S. (from the Physiological Laboratory 

 of University College, London). Received February 13, 

 1889. 



Although hitherto most physiologists have considered that the 

 pulmonary vessels probably possessed a system of vaso-motor nerves, 

 yet no direct experimental proof of the existence of such a system 

 has been obtained. Still less has any evidence been adduced to 

 demonstrate the actual anatomical paths by which such nerves, if 

 they exist, reach the lungs. Hence it seemed that the whole question 

 was one deserving a further attempt for its solution. When this 

 research was commenced, there were practically only two facts which 

 could be appealed to in support of the existence of these nerves. 



Firstly, Lichtheim observed that in asphyxia a rise of blood-pressure 

 may occur in the pulmonary artery unaccompanied by any rise in the 

 aorta. 



Secondly, it has been shown that in the frog, irritation of the skin 

 causes a contraction of the pulmonary vessels. 



It is clear that this second fact could not be used as an argument in 

 support of the existence of these nerves in the mammal, since the 

 anatomical relations are so different in the two cases. 



With regard to Lichtheim's observation, it is evident that it affords 

 no very direct proof, since other conditions, such as venous distension, 

 might easily account for the rise of pulmonary pressure. 



It was felt by us that the only really reliable method would be to 

 excite one by one the roots of the spinal nerves, and to observe the 

 effects of such stimulation on the aortic and pulmonary blood- 

 pressures simultaneously. 



The following method was employed : A cannula, placed in the 

 carotid artery in the usual manner, was connected with a mercurial 

 manometer. In a similar manner a second mercurial manometer was 

 then connected with the branch of the left division of the pulmonary 

 artery distributed to the lower lobe of the left lung. This vessel was 

 reached from the back by resecting portions ol two or sometimes 

 three ribs. In this way a record of the pressure in the left division 

 of the main artery was obtained, and also a means of detecting 

 changes of pressure in the main artery. At the same time, the 

 minimum amount of lung tissue was thrown out of gear. 



The upper dorsal nerves were then exposed inside the spinal canal, 

 and were ligatured outside the dura mater. By cutting through the 



