1895.] Nature and Physiological Action of Black-damp. 251 



cent, of carbonic acid. There was no smell of sulphuretted hydrogen 

 or any other gas. Two or three inspirations were sufficient to pro- 

 duce marked increase in the depth and frequency of the respirations. 

 The hyperpncea rapidly became more intense and was accompanied 

 by palpitations. At the same time I was observed to become blue in 

 the face. Within about thirty seconds I felt that I was becoming 

 confused, and did not push the observations further. Two or three 

 seconds after I had ceased to breathe from the pipe the blueness was 

 seen suddenly to disappear from my face and lips, and to be replaced 

 by the natural colour. 



The feelings which I experienced after the first fifteen or twenty 

 seconds in breathing the black-damp were distinctly such as are pro- 

 duced by breathing air very poor in oxygen. From previous experi- 

 ments I had become familiar with the distinction between the feelings 

 produced by excess of carbonic acid and those due to deficiency 

 of oxygen. The experiment of breathing the black-damp was re- 

 peated twice in order to leave no doubt. An analysis of the black- 

 damp gave the following result : 



Nitrogen 82'56 



Oxygen 1'45 



Carbonic acid 1O64* 



Methane 5*35 



Total 100-00 



I tested part of the mixture for carbonic oxide by shaking with a 

 little very dilute blood. Neither with the spectroscope nor by the 

 change of tint could I discover any, evidence of the presence of 

 carbonic oxide. The test employed would have detected 0'05 per 

 cent. The oxygen was determined by absorption with alkaline pyro- 

 gallate solution of the composition recommended by Hempel. The 

 methane was determined by explosion in a Hempel's explosion 

 pipette, after the addition of oxygen and detonating gas. All the 

 measurements were made over mercury. The gas-burette was a 

 modification of that of Petterson. 



The calculated specific gravity of this mixture is 1'0106, or very 

 nearly that of air. The extra nitrogen and the methane are both 

 considerably lighter than the oxygen which they replace, and thus 

 counterbalance the effect on the specific gravity of the heavier 

 carbonic acid. 



* A second determination of tlie carbonic acid gave exactly the same result 

 (10-64). 



T 2 



