538 EFFECT OF CUTTING OFF THE BLOOD FROM THE BE A IN. 



in 1861, I concluded that the sense of want of air, oi* the respiratoiy sense,, 

 was due to a want of oxygen in the general system, producing an impres- 

 sion which was conveyed to the medulla oblongata and which gave rise to 

 respiratory efforts; that, in ordinary respiration, this reflex action took 

 place unconsciously, but became exaggerated when there was a great defi- 

 ciency of oxygen, and was then experienced as a sense of suffocation ; that 

 the respiratory sense thus had its origin in the. general system and had 

 nothing to do with the lungs, as the sense of thirst has its seat in the general 

 S3^stem, from deficiency of water, and has simply a local manifestation in 

 dryness of the throat and fauces. In addition to the experimental argu- 

 ments in favor of this view, I saw, in cases of distress in breathing from de- 

 ficient circulation, as in certain cases of disease of the heart in which the 

 lungs are normal, what seemed to me to be a confirmation of my opinion, 

 . The views which I have just stated were advanced by me in my work, 

 " Physiology of Man," New York, 1866, vol. i., page 479, ef seq., and in my 

 " Text-Book of Human Physiology," New York, 1876, page 164. et seq. In 

 February, 1874, 1 made an address before the New York Society of Neu- 

 rology and Electrolog}^ upon the "Mechanism of Eeflex Nervous Action in 

 Normal Eespiration," an abstract of which was published in the JS'ew York 

 Medical Journal., in April of the same year. The full text of this address 

 was published in the Chicago Journal of Nervous and Mental Diseases, in 

 April, 1874. In this, I still adhered to my original view, and I extended 

 my reflections to the theory of the cause of the first respiration at birth, 

 respiration by means of the placenta in utero, etc. 



At the present day nearly all physiological writers agree that ihe sense 

 of want of air is due to want of oxygen, and not to any stimulating or irri- 

 tating properties of carbonic acid ; and this idea has received complete con- 

 firmation from the experiments of Pflliger upon the effects of respiration of 

 nitrogen, as is seen by the following extract : 



"Using blood-letting for ascertaining the condition of the blood during 

 dyspnoea, I arrived at the following facts : As soon as the dog begins to 

 breathe pure nitrogen, it is scarcely fifteen seconds before he makes violent 

 and deep inspirations ; at the end of thirty seconds, the most intense dys- 

 pnoea is observed, the blood is already almost absolutely black, w^iich must 

 be due to the enormously-rapid tissue-metamorphosis of this animal."^ 



It is seen that this experiment, made in 1868, is almost identical in idea 

 and results with those which I made in 1861, except that Pfliiger made his 

 animal breathe a gas not capable of supporting respiration, while I simply 

 deprived animals of air. Nearly the same experiment as that performed 

 by Pfliiger was made by Eosenthal, in 1862, who noted that animals suffered 

 no dyspnoea when air or oxygen was forced through the lungs, but that 

 dyspnoea was manifested when nitrogen or hydrogen was iised instead of 

 oxygen.f 



* Pfluger, "Ueber die Ursache der Athembewegungcn, sowie der Dyspno?^ uad Apnte." 

 — Arehivfur die gesammte Physiologie, Bonn, 1868, Bd. i., S. 89. 

 t Kosenthla, " Athembewegungen." etc., Berlin, 1862, S. 4. 



