EFFECT OF CUTTING OFF THE BLOOD FROM THE BRAIN. 539 



While physiologists ai-e now pretty generally agreed that the sense of 

 want of air is connected with a deficiency of oxygen in the blood of the 

 arteries, some writers are of the opinion that the ''sense" is primarily 

 due to a want of oxygenated blood circulating in the medulla oblongata. 

 This opinion has been advanced by some authors, but, as far as I know, it 

 rests mainly upon theory, and^has no positive experimental foundation. 

 Since I made the experiments which form the basis of this article, I have 

 consulted a number of systematic works upon physiology, with reference to 

 the subject under consideration. Most of the works examined contain no 

 very definite allusions to the res23iratory sense, or at most only brief and 

 unsatisfactory statements: but, in two, I find the following references, 

 which are directly pertinent to the question : 



" The first respiratory effort of the foetus is thus produced by the inter- 

 ruption of the placental re8j)iration, the sudden deficiency of the oxygen 

 and increase of carbonic acid in the blood (Schwartz). This change in the 

 blood needs to take place locally only in the vessels of the medulla ob- 

 longata, in order to produce this effect ; it occurs, for example, from arrest 

 of the blood in these vessels (by ligature of the carotid arteries, Ivussmaul 

 and Tenner, Eosenthal, or by closure of the venous currents from the brain, 

 Hermann and Escher), by which their blood becomes progressively poorer 

 in oxygen and richer in carbonic acid" (Hermann, "Grundiss der Physiolo- 

 gie des Menschen," Berlin, 1870, S. 160). 



"If the supply of blood be cut off from the medulla by ligature of the 

 blood-vessels of the neck, dyspnoea is produced, though the operation pro- 

 duces no change in the blood generall}^, but simply aftects the respiratory 

 condition of the medulla itself, by cutting off its blood-supply, the imme- 

 diate result of which is an accumulation of carbonic acid and a paucity of 

 available oxygen in the protoplasm of the nerve-cells in that region ' (Fos- 

 ter, "A Text-Book of Physiology," London, 1877, p. 254). 



These quotations from Hermann and from Foster show clearly that their 

 idea is, that the sense of want of air is due to deficiency of oxygenated 

 blood in the medulla oblongata, a view fully sustained by m.j own experi- 

 ments. The observations of Kussmaul and Tenner, referred to by Her- 

 mann, were made with reference to the cause of the convulsions which so 

 often occur after profuse and sudden hsemorrage. They are to be found in 

 the elaborate memoir by Kussmaul and Tenner, " On thel^ature and Origin 

 of Epileptiform Convulsions, caused by Profuse Bleeding," translated and 

 published by the "New Sydenham Society," in 1859. Kussmaul and Ten- 

 ner made a large number of experiments upon rabbits and horses, in which 

 they observed the effects of tying the great vessels given off from the arch 

 of the aorta. They noted, after this operation, great difficulty in respira- 

 tion and violent convulsions. They did not, however, abolish the respira- 

 tory movements of the animal by artificial respiration, thus abolishing, for 

 the time, the respiratory sense, and then note the effect of ligature of these 

 vessels. The experiments by Rosenthal, which are referred to, are proba- 



