114 Mr. W. F. Barrett on a Physical 



The deflections are not given in this Table, because the absorp- 

 tions are the mean of two or more experiments. The first bag 

 was now emptied of the remaining breath it contained and cleansed 

 with dry air ; it was then filled from the lungs by Dr. Frankland, 

 after he had undergone considerable exertion. The absorption 

 by this breath is given in the fifth column of Table V., a chemi- 

 cal analysis of it being also made by Dr. Frankland. In the 

 next Table the absorptions by air from the four bags are col- 

 lected together and can be seen at a glance. 



Table V. 



Tension, in 











inches. 



Bag No. I. 



No. II. 



No. III. 



No. IV. 



1 . . 



. 10-2 



10-7 



11-8 



12-1 



15 . . 



. 47-2 





48-7 



50-0 



30 . . 



. 50-6 



52-8 



537 



54-0 



The analysis made by Dr. Frankland gave the following results 

 as the percentage amount of carbonic acid contained in the seve- 

 ral bags : — 



Table VI. 



Air from the lungs 

 Carbonic acid per cent, in taken 



Bag No. I. . . 4*311 before breakfast. 



„ II. . . 4-556 after breakfast. 



„ III. . . 4*061 after walking. 



„ IV. . . 5*212 after severe exertion. 



By comparing in each case the absorption given in Table V. 

 with the analysis in Table VI., relative correctness is evident 

 with one exception, namely that of bag No. III. An error 

 from some cause must have arisen here, as an inspection of the 

 two Tables shows that, whereas in all the other cases increase in 

 absorption accompanies increase in the amount of carbonic acid, 

 this bag is found to have a medium absorption, but, according to 

 Dr. Frankland, contained the least amount of carbonic acid. The 

 error may have been caused by the substance of the bag itself, 

 which was different from, and newer than, the other two that 

 were used. This bag was therefore rejected to avoid in future 

 any chance of error, and in subsequent experiments the two other 

 bags, which had been repeatedly tested, were adhered to. 



A series of experiments was now commenced with a view of 

 making quantitative measurements of the carbonic acid in breath. 



This was thought to be easily accomplished by admitting into 

 the exhausted tube a known quantity of pure carbonic acid until 

 a deflection was obtained corresponding to that produced by the 



