EFFECT OF CUTTING OFF THE BLOOD FROM THE BRAIN. 541 



tained. Over the valve of the bellows was placed a sponge, which wa& 

 saturated with ether from time to time, so that the animal was kept com- 

 pletely ansesthetized during the experiment. The air in the bellows was 

 also changed from time to time by pushing up the valve with the fingers 

 and forcing out the vitiated air. The chest and abdomen were then laid 

 open b}^ a continuous incision in the median line, and the ribs were bent 

 backward and secured Avith a strong cord tied behind the back, so that the 

 lungs and heart were fully exposed. The pericardium was then cut away, 

 the great vessels near the heart were isolated, and loose ligatures were 

 thrown around the trunk of the innominate artery, the left subclavian ar- 

 tery, the descending vena cava, the descending portion of the aorta, and the 

 ascending vena cava.-i^ In this way, I was prepared to constrict the several 

 vessels at will. 



When these preliminary steps had been completed, the animal being en- 

 tirely under the influence of ether and artificial respiration being kept up 

 efficiently, there were absolutely no respiratory efforts, and the diaphragm, 

 which was exposed, was quiescent. 



The artificial respiration Avas then arrested. In forty-five seconds, the 

 animal began to make violent respiratory efforts. Artificial respiration 

 was then resumed, and the respiratory efforts of the animal ceased. When 

 the artificial respiration was arrested, we first noticed a movement of the 

 corners of the mouth at regular intervals, and then the mouth was widely 

 opened and the diaphragm became strongly contracted, also at regular in- 

 tervals. The time was taken at the first violent respiratory effort. 



The animal being perfectly quiet and making no efforts at respiration, 

 the innominate artery, the left subclavian artery, and the descending vena 

 cava, were tied nearly simultaneously, artificial respiration being constantly 

 and efficiently maintained. In two minutes and eight seconds, the animal 

 began to make respiratory efforts, which continued as long as the vessels 

 remained constricted. 



The ligatures surrounding the vessels mentioned above were loosened 

 five minutes and twenty-two seconds after they had been tied, and the 

 respiratory efforts of the animal instantly ceased. After three minutes, arti- 

 ficial respiration was stopped, and the animal began to make respiratory 

 efforts in thirty-nine and a half seconds, which ceased as soon as artificial 

 respiration was resumed. 



The descending aorta and the ascending vena cava in the chest were 

 then tied simultaneously, the vessels arising from the arch of the aorta be- 

 ing free. This seemed to produce no effect, and no respiratory efforts were 

 made by the animal for five minutes. The innominate artery and the left 

 subclavian artery were then constricted, the aorta and ascending vena cava 

 remaining tied. Eespiratory efforts by the animal began in one mintite 



*In the dosr, the aorta gives off the innominate artery "which gives off first the lett 

 carotid, and then divides into the right subclavian and right carotid " (Foster, " Elementary 

 Practical Physiology," London, 1876, p. 13). The left subclavian artery arises directly from 

 the aorta. 



