540 EFFECT OF CUTTING OFF THE BLOOD FROM THE BRAIN. 



bly those contained in his work on "Die Athembewegungen und ihre Be- 

 ziehungen ziim Nervus Yagus," Berlin, 1862. In these experiments, as I 

 have already stated, it is shown that the respiratory efforts of an animal 

 can be abolished by forcing atmospheric air or oxygen in large quantities 

 through the lungs, but that the sense of want of air is felt when, in place of 

 ■oxygen, nitrogen or hydrogen is employed, by this means removing the 

 possibility of an irritation from carbonic acid. These are essentially the 

 same as the observations made by Pfluger, in 1868. Eosenthal states very 

 distinctly that the sense of want of air is due to want of ox^-gen-carrying 

 blood in the medulla oblongata ; but he does not actually demonstrate the 

 truth of this proposition by experiments. The statements by Hermann 

 and by Foster are apparently based upon the experiments of Kussmaul and 

 Tenner and of Eosenthal; but I must nevertheless claim that the experi- 

 ments which 1 have made upon this subject, which will be detailed farther 

 on, if thej^ should be confirmed, afford the first positive proof that the 

 respiratory sense nxSij be excited by cutting off the arterial supply from the 

 medulla. There is nothing which I can find, in the experiments of Kuss- 

 maul and Tenner or of Eosenthal, to actually show that the sense of want 

 of air is not due to a want of oxygen in thejgeneral system. 



In reflecting upon this subject during the last few months, it occurred to 

 my mind that the the question was capable of a positive solution by experi- 

 ment. If it be possible to cut off the arterial supply to the head and me- 

 dulla oblongata, leaving the rest^of the circulation free, an animal should 

 make respiratory efforts, even though air be supplied to the lungs, provided 

 that the sense of want of air be due to a want of oxygenated blood in the 

 medulla. On the other hand, if the sense of want of air be due to a want of 

 oxygen in the general system, cutting off the arterial supply from the head 

 and medulla would have no more effect than cutting off the supply of oxy- 

 gen from any other equally extensive part of the system. In reducing this 

 idea to the project of an actual experiment, I conceived the following : I 

 proposed to tie all the vessels that could by anj- means suppl}^ the medulla 

 oblongata with blood (the vessels given oft' from the arch of the aorta), and 

 note the efl'ects ; and then to tie the descending aorta in the chest, and note 

 the effects, leaving the vessels coming from the arch of the aorta free. It 

 seemed to me that, if the respirator}^ sense were due to want of oxygen in 

 the general system, tying the aorta in the chest would induce respiratory 

 eftorts certainl}' as promj)t]y as cutting off the arterial supply from the me- 

 dulla. With the view of settling this question, if possible, I made the fol- 

 lowing experiments, which, as far as they go, are exceedingly definite and 

 satisfactory in their results. I propose, however, to extend these experi- 

 ments, and I publish them now simply as preliminary to farther investiga- 

 tions into the subject under consideration : 



Experiment I., September 30, 1877. — A medium-sized, full-grown dog was 

 brought completely under the influence of ether. The trachea was then 

 opened and connected with a bellows, and artificial respiration was main- 



