144 



Dr. Johnson. On Asphyxia and 



[Feb. 



Any strip of elastic material will do for the above if the length be 

 suitable one readily finds the proper length by trying larger and 

 smaller circles. 



VI. "On the Physiology of Asphyxia, and on the Anaesthetic 

 Action of Pure Nitrogen." By GEORGE JOHNSON, M.D., 

 F.R.S. Received January 26, 1891. 



(Abstract.) 



The main object of this paper is to bring forward additional evidence 

 in support of the theory that the immediate cause of death in cases 

 of asphyxia is the arrest of the pulmonary circulation. I have 

 express my obligation to my friend Mr. Charles James Martin, MJ 

 B.Sc., Demonstrator of Physiology in King's College, for the time 

 labour which, by my request, he has bestowed in the performance of 

 numerous and various experiments, the results of which will, I thinl 

 throw much light upon the complex phenomena of asphyxia. It 

 right to mention that Mr. Martin is not responsible for my interpr 

 tion of the results of his experiments. 



All the experiments were performed on animals under the inflnc 

 of anaesthetics, and every animal was finally killed by deprivation 

 air. 



Animals rabbits, cats, and, in a few cases, dogs were asphyxiated 

 either by ligature of the trachea, by the paralysing influence of cnrara, 

 or by causing them to inhale a gas containing no free oxygen, viz., 

 nitrons oxide, pure nitrogen, hydrogen, and carbonic acid gas. In 

 all these experiments, re-inspiration of the gases was avoided by 

 allowing the expired gas to escape through a "J"'^ 11 ^ 6 fixed i Q the 

 trachea. 



During the performance of the experiments, in most cases, tl 

 chest and pericardium of the animals were opened so that the relative 

 fulness of the cavities might be readily observed. In all the experi- 

 ments, the results, as regards distension of the heart's cavities, were 

 essentially the same, no matter whether the air was simply exclude 

 or whether an azotic gas (i.e., a gas, not in itself poisonous, but 

 unable to support life) was substituted for atmospheric air ; the onlj 

 difference being that when an azotic gas is inhaled the phenomei 

 are far more rapidly produced, in consequence of the more speedj 

 displacement of oxygen from the lungs. 



The principal changes in the heart's cavities were, first, distensior 

 of the left cavities ; second, enormous distension of the right cavities 

 with diminished distension of the left, the circulation being apparently 

 arrested by the inability of the right cavities to empty themselves, in 



