CARBONIC ACID AND VENTILATION. 93 



whether there be 0*04 or 2 per cent, of carbonic acid in 

 the air^ and no matter although there be 20*94 or only 1 8 -8 of 

 oxygen. This is strongly corroborative of the views taken 

 by Liebig, but other circumstances tend on the other hand 

 to show that this state of things is kept up at the sacrifice 

 of the comfort J to say the least, of other vital functions. 

 There must of course be a limit, but I was afraid to go 

 farther than I went. In one experiment the breathing was 

 changed from 16 inspirations per minute to 22, the pulse fell 

 from 76 to 55, whilst it was so weak that it was difficult to 

 find. My assistant was in the chamber this time ; I re-; 

 quested him to attend to his pulse and breathing, as on 

 another occasion when there was still more carbonic acid 

 in the air, namely, 3*9 per cent., my breathing rose up to 

 26 inspirations, and my pulse became so weak as to cause 

 alarm. This has hajjpened so regularly that it must be put 

 down as the result of poisoning with carbonic acid. On 

 one occasion there was a comparatively large amount of 

 oxygen in the room, rvi. 20- 1. The carbonic acid had been 

 driven in upon fresh air, and no oxygen removed. Even 

 here the pulse was weak, although the breathing was not 

 very difficult, and the candles burnt moderately well. 

 - The conclusion is, that in the air containing an increased 

 amount of carbonic acid, this gas alone, even without the 

 other hurtful ingredients, such as organic matter, begins 

 to poison, and men exposed to it are really gasping for 

 breath without knowing it. All the other hurtful condi- 

 tions contribute their powerful aid. 



As I came on this result at the end of the inquiry into 

 the composition of the air of mines, it is not easy to do it 

 justice. We learn much from it. We learn that the blood 

 can take its oxygen out of very impiu-e mixtures ; but we 

 learn also that some functions are meantime suffering 

 greatly. It is, to my view, a most important thing to 

 show that with an amount of oxygen not less than is 



