Cantor lectures on climate in its relation to health / by G.V. Poore.

  • Poore, George Vivian, 1843-1904.
Date:
1885
Catalogue details

Licence: Public Domain Mark

Credit: Cantor lectures on climate in its relation to health / by G.V. Poore. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    5/44 (page 3)
    p. 436. “ A cubic foot of dry air at 30” Fahr. weighs 566'850 grains, and is thus constituted— 436‘475 grains of nitrogen. i30'375 ,, of oxygen. At a temperature of 80° Fahr. the foot of air weighs 5i6‘38 grains, and is thus com- posed— 397‘6i grains of nitrogen. 11877 »> of oxygen. 516-38 Thus, at the higher temperature (80° Fahr.), each cubic foot of air contains 11-605 grains of oxygen less than at the lower temperature, and if we assume that the rate and depth of I respiration is the same at the two tempera- tures, and if we further assume that i6-6 cubic ' feet of air are drawn into the lungs every hour, then the man in the tropical temperature, as ^ compared with the man in the Arctic tempera- ture, will have, so to speak, an hourly deficit of oxygen amounting to 192-6 grains. The fire burns bright, we are told, in frosty ' weather, the reasons being, firstly, that those ■ who have the care of the fire, and arc them- selves nipped by the frost, take care that it shall burn brightly ; and secondly, the cold air 1 which supports the combustion is rich in o.xygen. One of the great objects of respiration is to I support the animal heat, and it is only one of the many instances of the absolute adaptation i of means to ends which we meet with every- where in nature, that the man who is exposed ' to cold is supplied with increased amount of i oxygen, to cause a brisk combustion in the human furnace ; while he who is scorched by I the sun, and has less need of internal fire, gets I a diminished supply of oxygen. I Again, diminution of pressure lessens the [r amount of oxygen in each cubic foot of air. If we ascend a mountain 5,000 feet high, the I barometer will fall from 30 inches to 25 inches, a i e., the pressure will be diminished one-sixth, u and a cubic foot of air, which contained 130-4 t grains of oxygen in the valley, will contain only io8-6 grains at the higher level, or a diminu- K tion of 21-8 grains per cubic foot. If we » assume the rate and depth of respiration to : be unaltered (which we have no right to do) 9 then the deficit of oxygen at the higher level I per hour amounts to 21-8 X 16-6 = 361*88 E grains. These figures show that man is able J to bear very great fluctuations in the weight a of oxygen in the air which he breathes. They ( showcertainly more than this, viz., that fluctua- I tions in the amount of oxygen are necessary for his -well-being under variations of tempera- ture and pressure. Why it is that less oxygen is required to support life at great altitude is not very clear, but when we look at the hardy mountaineer, the type of health and manly beauty, we must admit that the fact is un- deniable. Although we are, at present, unable to say that the mere fapt of a small per-centage variation of o.xygen in the air breathed is, by itself, a very important matter, still we have to remember that it is never an isolated fact, and has always to be considered along with other facts. What we have to look to is the reason why a diminution has taken place. Whether the small amount of carbonic acid (•04 per cent, by volume) which is present in the air serves any useful purpose in the anima economy, it would be difficult to say. Carbonic acid is regarded as an impurity, an impurity poured into the air as the result of respiration and combustion. In the open air the amount is not found to vary to any very great extent, as the following list will show :— Carbonic Acid, per CenI’. Over open sea (Thorpe) -032 At Manchester (A. Smith) -037 At Portsmouth (De Chaumont) .... -032 At Aldershot ,, .... -0.10 At Tower of London ,, .... -042 At Chelsea ,, .... -047 At Paddington ,, .... -056 At Munich (Pettenkofer) -050 Top of hlont Blanc (Franldand) .... -o6i At Chamonix „ .... -063 Arctic Regions, Alert (Moss) -055 It is well known that carbonic acid in large quantities is a narcotic poison. An atmo- sphere containing from 5 to 10 per cent, {i.c., 100 to 200 times the amount in ordinary air) is fatal. It is stated that in soda-water factories, where the amount of carbonic acid often reaches -2 per cent., no ill-effect is felt. The variations in the carbonic acid in the air are not very great; and it is probable that variations such as those shown above of car- bonic acid per cent., would bo incapable of working much, either for good or ill, but it must be remembered that carbonic acid always keeps bad and dangerous company ; and when the chemist tells us that in such or such a place carbonic acid which he can analyse is in excess, we may feel sure that it