EFFECT OF CUTTING OFF THE BLOOD FROM THE BRAtN. o37 



MEDICINE AND HYGIENE. 



Experiments on the Effects upon Respiration of cutting off the 

 Supply of Blood fronn the Brain and Medulla Oblongata. 



BY AUSTIN FLINT, JR., M. D., 



Trofessor of Physiology in the Bellevue Hospital Medical College, New York, etc. 



In October, 1861, I published in the American Journal of the 'Medical 

 Sciences a paper on "Points connected with the Action of the Heart and 

 with Respiration." In this paper, I contended that the respiratory sense 

 {besoin de resjnrer of the French), or sense of want of air, which gives rise 

 to the movements of respiration, is due to a want of oxygen in the general 

 system. I assumed that the medulla oblongata is the center presiding over 

 the respiratory movements ; that these movements are reflex; that a cer- 

 tain sense, called the respiratory sense, is conveyed to the medulla ob- 

 longata ; and that it is this sense which is the starting-point of the respira- 

 toiy acts. I showed that a dog brought under the influence of ether, with 

 the heart and lungs exposed and with a bellows in the trachea, will make 

 no respiratory efforts so long as air is efficiently supplied to the lungs by 

 artificial respiration, an experiment essentially the same as one made by 

 Iiobert Hook, in 1664. In an animal in this condition, I showed that respir- 

 atory efforts wei'c made, when artificial respiration was interrupted, as soon 

 as the blood became dark in the arteries, having opened an artery and 

 noted the color of the blood as the cx2)eriment progressed. 



It seemed to me at that time that the sense of want of air in this experi- 

 ment was due to the properties of the dark-colored blood circulating in the 

 arterial system ; and the question arose in my mind whether this were de- 

 pendent upon the deficiency of oxygen in the blood or upon the presence of 

 carbonic acid. In order to answer this question, I drained an animal (a 

 good-si^ed dog) of blood by dividing the femoral artery, the chest having 

 been opened with the animal under the influence of ether, and artificial 

 respiration being maintained in the usual way. In this experiment, although 

 the lungs were constantly supplied with air, violent respiratory efforts were 

 made as the animal became nearly exsanguine. 



In another experiment, I divided both p^icuraogastric nerves and ascer- 

 tained that there was no difference in the phenomena observed, showing 

 that these nerves are not the sole conductors of the sense of want of air, if, 

 indeed, they have any part in this function. In still another experiment, I 

 drained an animal of blood by cutting out the heart. This was followed by 

 violent respiratory efforts, showing that the sense of want of air has noth- 

 ing to do with distension of the right cardiac cavities. 



From the experiments of which I have thus given a brief sketch, made 



