2 
DE. W. MARCET ON A CHEMICAL INQUIRY INTO 
(o.) Instead of an increase, there is rather a reduction in the weigdit of the air 
breathed by removing higher and liigher above the sea level. 
(6.) The absolute and relative quantity of carbonic acid exhaled from the lungs 
increases by removing into higher regions, although there be no change in the 
respiratory frequency ; at the same time the weight of the air breathed is reduced. 
Dr. Mermod’s investigations were undertaken at two stations only, one of them being 
Strasburg, at an altitude of 142 metres, and the other Ste. Croix, at 1100 metres; 
the difference of altitude amounting therefore to the small figure of 958 metres. 
Thirty-five experiments were made at Strasburg, and thirty-two at Ste. Croix, on the 
volumes of air breathed and weights of carbonic acid expired. The mean barometric 
pressure was 744‘89 mm. at Strasburg, and 669'2l mm. at Ste. Croix, giving a difference 
of 75’68 mm. The extent of the inquiry appears hardly sufficient to determine the 
influence of atmospheric pressure on the chemical phenomena of respiration, but the 
work is evidently well done, and I feel called upon to discuss it in some of its 
beariiiP’s. 
O 
On one point I agree with Dr. Mermod, that there is a reduction in the weight of 
air breathed within a given time at increasing altitudes, and depending on atmos¬ 
pheric pressure alone. My experiments, which extend to altitudes of 3300 and 4000 
metres, some of them made under circumstances doing away with the influence of cold, 
certainly yield that result. I have expressed this law by stating that there is, at in¬ 
creasing altitudes, a reduction in t he volume of air breathed, reduced to 0° and 760 mm. 
Dr. Mermod’s sixth and last conclusion deals with the amount of carbonic acid 
exhaled from tlie hmo;s within a o-iven time at different altitudes. At first I was 
disposed to conclude with him, that more carbonic acid is expired as the atmospheric 
pressure falls from increasing altitude, as I found that more carbonic acid was exhaled 
per minute in the mountains than in the plains; but it occurred to me that the increased 
cold experienced on ascending in the Alps was not unlikely to exert an influence on 
this phenomenon, and that the excess of carbonic acid expired in Alpine disfricts might 
be due to cold and not to rarefied air. My experiments, made on the peak of Tenerife, 
in order to clear up this point, showed conclusively that when no cold is experienced on 
reaching higher levels, there is no increase in the amount of carbonic acid expired 
within a given time. 
Dr. Mermod does not lose sight of the question of temperature, as he records 
the temperature of the atmosphere at the time of every experiment, and he finds 
that the mean of all the temperatures observed was the same at both stations. 
At his lower station, his mean temperature is 12°'65 C., and at his higher station, 
12°'68 C. He thus disposes of any influence due to differences of temperature. 
The effect of food is done away with by making the experiments between 7 and 8 
o’clock in the morning, and before breakfast. The barometer reading is recorded at 
the time of every experiment, but it is much to be regretted that the author quotes 
no hygrometric observations. 
