598 



the diminishing influence of the respiratory efforts on the heart. 

 It would be easy to show that the influence of the inspiratory effort 

 on the central organ of circulation is comparable to the change 

 taking place in the pupil when the globe of the eye is drawn inwards : 

 it is an associated action. 



From the facts I have found in the case of newly -born animals and 

 birds, and from the facts observed in man by Professors J. Mueller, 

 Bonders, and others, it results that, during efforts at inspiration, a 

 nervous influence passes along the par vagum from the medulla 

 oblongata to the heart, diminishing the movements of this organ. 

 And as by an action of our will we may inspire with energy, it 

 follows that we can by an influence of our will diminish the action 

 of our heart, just as we can contract our pupil by drawing our eyes 

 inwards. 



V. "Summary of a Paper (to be presented) on the Influence 

 of Oxygen on the vital properties of the Spinal Cord, 

 Nerves, and Muscles." By E. BROWN-SEQUARD, M.D. 

 Communicated by JAMES PAGET, Esq., F.U.S. Received 

 June 25, 1857. 



The influence of oxygen and carbonic acid on the living tissues, 

 has been very little investigated, either by physiologists or practi- 

 tioners of medicine. I have made a great many experiments on 

 this subject, but will relate here merely a few of them, which are 

 sufiicient to show that oxidation of the spinal cord and nerves, as 

 well as that of muscles, increases their vital properties, sometimes 

 in a high degree. 



After the opening of the spinal canal, the dura-mater being laid 

 bare, we find that an evident hypersesthesia appears after a short 

 time in the parts of the body which are behind the opening, and 

 also on the same level with it, and a little above it. I think 

 this increase of sensibility depends on the absorption of oxygen. 

 To ascertain that it is so, with the help of a special apparatus, im- 

 mediately after laying bare the cord, I pump out the air in contact 

 with the dura-mater, and substitute for it hydrogen. Then I find 



