246 On the Changes produced in Atmospheric Atr 



The breathing in. these cases was as nearly natural as we 

 conceive it possible to be in any apparatus ; the operator was-- 

 scarcely fatigued, and his pulse not raised more than about 

 one beat in a minute; the respirations however were deeper 

 and fewer than natural, amounting only to about 58 in eleven 

 minutes, whereas from repeated observations at different and- 

 distant times he makes 10 in a minute. The smallness of 

 the deficiency surprised us very much, as, from the reports 

 of other experimenters we had been prepared to expect a 

 much greater loss. It might be objected that the air was 

 rarefied by passing through the lungs ; but this was almost 

 immediately counteracted by the mass of quicksilver in the' 

 gasometers, which amounted at least to one hundred and 

 fifty pounds j and we have repeatedly noticed, that air under 

 these circumstances has suffered no perceptible diminution 

 by standing for a considerable time ; in one case, in which 

 air from the Inncs was driven into the mercurial gasometers 

 for twenty- seven minutes, the temperature of the quick- 

 silver at the end of the experiment was not raised half a de- 

 gree of Fahrenheit's thermometer. The deficiency, in our 

 opinion, principally arises from the difficulty in bringing the 

 lungs precisely to the same state after, as before the expe- 

 riment ; and it must be recollected that the operator com- 

 menced by a forcible expiration into the open air, but finish- 

 ed by a forcible expiration into the mercurial gasometer. 

 Now, although this gasometer was counterpoised by weights 

 in the scale attached to it, yet we can easily conceive that 

 more resistance might be afforded to the complete evacuation 

 in the latter case than in the former, and consequently the 

 lungs might contain a few inches more after the experiment 

 than before it, which might in some measure account for 

 the deficiency. 



In the eleventh experiment, portions of gas were taken off 

 from each of the mercurial gasometers as they were filled^ 

 and these portions being afterwards mixed were carefully 

 examined. 'Eleventh Experiment. 



_, Cubic inches .-, , . • , 



_ Thennom. ~- c ■ Cubic inches -,-. r . 



Barom. t- . Time. 01 common air .T D i-ed Deficiency- 



inspired. c ° " 



30*4 §0° Uram, 3460 343f 23 



To 



