CARBONIC ACID AND VENTILATION. 101 



applied to smaller amounts of carbonic acid, the following 

 experiments were made. In them the organic matter is 

 entirely excluded. For the first, in which i per cent, of 

 carbonic acid was mixed with the air, several aspirators of 

 flexible material were filled with the mixture, and the air 

 was inhaled from the aspirators by the mouth, whilst it was 

 exhaled from the nostrils. The carbonic acid was made 

 from bicarbonate of soda, and passed through a solution of 

 bicarbonate of soda to remove mineral acids. 



With I per cent, of Carbonic Acid. 



After 2 minutes 67 



.. 4 .. 67 



„ 6 „ 68 



» 8 ., 67 



„ 10 „ 68 



„ 12 „ 67 



Pulse. Pulse. 



66 After 14 minutes 66 



16 „ 64 



18 



20 

 22 

 26 



64 

 64 

 63 



63 



In this experiment the difficulty of supplying air was felt 

 to be considerable ; and the aspirations having become less 

 agreeable and regular, they were not counted. 



In order to remove all difficulty, the lead chamber was 

 charged with the mixture to be breathed, and the operator 

 sat outside inhaling the air through a wide tube with ease. 

 Of course a similar amount of air entered, and this was 

 supplied through some small chinks, which were not care- 

 fully filled up. The change takiag place in the air of the 

 chamber from this latter cause only would scarcely be 

 perceptible in half an hour, and then it would be against 

 the success of the experiment. The uniformity of results 

 is therefore very remarkable. 



