2 76 Prof. Tyndall on the Absorption and 



sometimes necessary to perform this operation daily, and never 

 on any occasion Lave I used tubes to dry a feeble gas which had 

 been previously used to dry a powerful one. 



In the present communication I shall have to touch upon 

 many subjects which for want of time I have been unable to 

 develope. The following is an example of these. Choosing a 

 day of suitable temperature and moisture — a day on which the 

 human breath shows no signs of precipitation — the action of the 

 substances expired from the lungs may be most strictly deter- 

 mined by our apparatus. By breathing directly into the expe- 

 rimental tube, the action produced by the sum of the products 

 of respiration might be accurately measured; by breathing through 

 the sulphuric-acid tube, the moisture of the breath would be with- 

 drawn, and the difference between the action then observed and 

 the former action would give that of the carbonic acid. In this 

 way the products of respiration might be estimated singly, and 

 the influence of various kinds of food and drink, or of physical 

 exertion, on the respiration might be investigated in a manner 

 hitherto unthought of. 



I have to record the following experiments only in connexion 

 with this subject. Placing a suitable tube between my lips, I 

 filled my lungs with air ; a stopcock which was interposed between 

 me and the experimental tube being partially opened, I breathed 

 through it slowly into the latter until the mercury gauge of the 

 pump was depressed 15 inches. I had, at the time, two assist- 

 ants, C. A. and R. C, and they subsquently breathed into the 

 experimental tube the same quantity as myself. In the follow- 

 ing Table the absorption produced by the breath of each is 

 stated : — 



Action of the Products of Respiration on Radiant Heat. 



Initials of 





Initials of 





person's name. 



Absorption. 



person's name. 



Absorption 









J. T. . . 



. . 59 



J. T. 





. . . 62 



R. C. . . 



. . 63 



R. C. 





. • . 66 



C. A. . . 



. . 62 



R. C. 





. . . 68 



J. T. . . 



. . 60-5 



J. T. 



again . 



i • ■ o . J 







The absorption of dry air on the day that these results w r ere 

 obtained was found to be 1. The same dry air inhaled, underwent 

 a chemical change which augmented its absorptive energy at least 

 60 times. I give this as a minor limit, and will not say how 

 much I regard it as falling short of the truth. 



The day afterwards the following results were obtained, the 

 same amount as before being exhaled : — 



