516 Dr. W. Marcet on the Function of Respiration at [Apr. 24, 



The few experiments I succeeded in completing at that spot, showed 

 an evaporation of water from the lungs above that expired at the sea- 

 side, equal to 0*141 grm. per minute, or 43"5 per cent. 



If the weight of moisture expired at the three principal stations be 

 considered together with the altitudes of the stations, a certain relation 

 will be found to exist between them ; this relation is established in 

 the following table, showing what the proportions of humidity 

 expired would amount to if calculated with reference to the barome- 

 trical pressures. These figures are entered in the column of the 

 following table headed Theory. 



Water Expired. 



Barometer, 



Theory, 



Found. 



Difference. 



Puerto. . . . 760 niillims, 

 Gruajara . . . 594 '4 „ 

 Alta Vista. 521-4 „ 



0-183 grm. 

 -234 „ 

 0-267 „ 



0-183 grm. 

 247 „ 

 0-314 „ 



5 per cent. 

 15 „ 



The results obtained show, therefore, that the evaporation of 

 moisture from the lungs increases as the barometer falls. The ratio 

 is, however, no more than approximate. I question whether a similar 

 result would be obtained in the Alps, where the cold at certain heights 

 must exert a considerable influence on the evaporation from the lungs 

 and air passages. 



Besults from the Investigation,* 



The results I have obtained from my experiments on the Island of 

 Teneriffe may be expressed as follows : — 



1. The mean of the whole amount of the carbonic acid expired at 

 the three stations (the experiments at the foot of cone not included) 

 in the sitting posture, and determined from 60 experiments in my 

 case and 55 in that of the guide, was proportional to the weights 

 of our bodies respectively, and amounted to 676 mgms. per 100 kilos, 

 for each of us. 



2. The mean weight of the whole carbonic acid expired at the three 

 stations while engaged with the same amount of measured muscular 

 work, and determined from 18 experiments .for each of us, was 

 respectively proportional to the weights of our bodies. 



3. The mean weight of carbonic acid expired by both of us 

 (with one exception only) was highest during the first or second hour 

 after a meal, while it diminished by degrees as time elapsed since food 

 was taken. This agrees with my results obtained in the Alps. 



4. The mean weight of carbonic acid expired by myself on the 



