148 Dr. Johnson. On A*j>/ti/.i-<'t //<</ the [Felt. .3, 



Conclusions relating to Asphyxia. 



That the immediate cause of death is the arrest of the pnlmonu y 

 circulation appears to be proved by the following facts : 



1. When the chest of au animal is opened immediately after death 

 caused by a ligature on the trachea, the right cavities of the heart 

 are found enormously distended, while the left are comparatively 

 empty. 



2. When the heart of an animal is exposed during the progress of 

 asphyxia, the right cavities are seen to become distended, while the 

 left, which had been previously gorged, are found to be collapsed and 

 nearly empty. 



3. In the last stage of asphyxia there is a continuous increase of 

 pressure in the pulmonary artery while the systemic arterial pressure 

 is falling. 



4. That the arrest of the circulation through the lungs is due to 

 the contraction of the pulmonary arterioles appeal's to be proved by 

 the influence of agents which paralyse the arterioles, namely, nitrite 

 of amyl, atropine, and an excessive dose of curara ; the effect 

 which is that deprivation of air is unattended by distension of the 

 right cavities of the heart and other evidence of obstructed pulmonary 

 circulation, the life of the animal is prolonged for several minutes, 

 and death ultimately results from the influence of venous blood upon 

 the cardiac and nervous tissues. 



The anesthetic action of nitrogen alone or with a small proportion of 

 oxygen. The phenomena which result from the inhalation of nitrous 

 oxide as an anaesthetic are strictly analogous with those observed in 

 the early stages of asphyxia.* 



Some writers maintain that the anaesthetic action of nitrous oxide 

 is due to its preventing access of free oxygen to the system, others 

 believe that it has a specific anaesthetic action. It occurred to me 

 that light might be thrown upon this subject by the administration 

 of pure nitrogen. Accordingly I obtained from the Scotch and Iris 

 Oxygen Company, of Glasgow, a cylinder containing 100 cubic feet < 

 compressed nitrogen in which the proportion of oxygen was onlj 

 0'5 per cent, by vol., whilst that of the CO 2 present was 0'3 per cent. 

 As a preliminary trial, Mr. F. W. Braine was good enough to admin- 

 ister this gas in five instances to members of the staff of King's 

 College, who volunteered to inhale it. 



The result was, in each case, the production of complete anaesthesia 

 and of general phenomena precisely similar to those observed from 

 the inhalation of nitrous oxide. Encouraged by theee results, Mr. 



* Tide the author's ' Essay on Asphyxia,' p. 30. 



