September 28, 188:3.] 



SCIEyCE. 



4->9 



It is known, also, that tlie transpiration of 

 gases through tubes, which the bronchi really 

 are, is hindered by a diminution of pressure, 

 and that in consequence of this, in a given 

 time, under the same conditions of expansion, 

 etc., less air will enter the lungs at .5,000 feet 

 elevation than at sea-level. This is another 

 cause why the respirations should be either 

 deeper or more frequent. 



It is fiu'thcr known that the osmose of gases 

 through a thin septum, as in the lungs, is less 

 rapid the less the pressure, or, in other words, 

 that the rapidity of the osmose of gases is de- 

 pendent upon the pressure to which they arc 

 subjected. This being so, as the density of 

 the oxygen and carbonic acid in the lilood is 

 nearlj- constant, if the density of these gases 

 in the air be diminished, there will be an effect 

 produced upon the rapidity of their osmose. 

 In the case of oxygen, it is claimed that an 

 individual will get less of it at 5,000 feet ele- 

 vation than the system requires, and that, un- 

 less the conditions of respiration be changed, 

 there will be a ' starvation of oxygen,' i.e., an 

 asphyxia. In consequence of all this, it has 

 been claimed .that a greater depth and fre- 

 quency of respiration is demanded to meet 

 this want. 



In regard to the osmose of oxygen, we know, 

 that, even though there be a hindrance due to 

 the diminished density of the gas in the air, 

 there is still, on the other hand, an increased 

 rapidity of the circulation, which would favor 

 osmose ; and it ma\- be assumed that tlie effects 

 of these two conditions counterbalance one 

 another. 



In regard to a starvation of oxygen being 

 produced by a diminution in the amount of the 

 gas at a higher elevation, the rationale is some- 

 what as follows : there exists in the atmos- 

 phere, under all pressures, 23 parts by weight 

 of oxygen. At sea-level, there are 130.4 grains 

 of the gas in every cubic foot, while, at 5,000 

 feet, this amount will be diminished one-sixth, 

 so that there will only be 108.6 grains to the 

 cubic foot. The (juestion then is, whether a 

 density of 108. G grains to the cubic foot of air 

 will produce a starvation of the gas in the 

 human economj-. 



It has been estimated that the tension of 

 the oxygen of the venous blood of the dog is 

 2.9%, or 22 mm., of mercury. It has been 

 further estimated that tlie tension of the oxy- 

 gen of the pulmonary air-cells is at least 10% 

 of the atmospheric pressure, which, at 5,000 

 feet, would amount to 1)3.3 mm. of mercury ; 

 so that it is evident, that, even under this 

 diminution of pressure, the difference between 



the density of the oxygen in the inspired air 

 and in that of the venous blood brought to the 

 lungs is sufficiently groat to admit of a free 

 osmose. 



Further than this, we know that the amount 

 of tidal air passing in and out of the chest of 

 an average man is 500 cc, or 31 cubic inches. 

 Allowing 17 respirations to the minute, this 

 will make 510 litres, or 18 cubic feet, of oxy- 

 gen inspired per horam. At 5,000 feet this air 

 would contain 1,955 grains of oxygen. Now, 

 the absolute absorption of oxygen at sea-level 

 is only five per cent of that contained in the 

 air, and the amount that is absolutely needed 

 each hour, at sea-level, is only 117 grains. As 

 the absolute demand for oxygen is only 117 

 grains each hour, and as the actiial amount 

 contained in the inspired air at an altitude of 

 5.000 feet is, for the same time, 1,955 grains, 

 it is evident that here, .again, the suppl3' is 

 greatly in excess of the demand, and tiiat the 

 term ' starvation of oxygen,' as explanatory of 

 the increased depth and rapidity of the inspira- 

 tions at high altitudes, is a misnomer. 



But in addition to the absorption of ox^-gen 

 there is the elimination of carbonic acid to be 

 accounted for. It is evident, that, as the ten- 

 sion of the gas in the venous blood coming 

 to the lungs is nearlv constant, anv diminution 

 of its tension in the air will favor its osmose 

 from the blood to the air, and that the effect 

 produced upon the osmose of this gas by rise 

 of elevation is the reverse of the effect upon 

 the osmose of oxygen. 



In concluding this part of our subject, we 

 wish to emphasize the fact that we think that 

 the benefit to be derived from simple elevation, 

 in cases of phthisis puhnonalis, is to be attrib- 

 uted largelj- to the greater depth of the in- 

 spirations, and consequentl}' to the greater 

 distension and activity of all parts of the 

 lungs (the diseased apices as well as the 

 healthy bases), and to the increased elimina- 

 tion of morbid products brought about b^- the 

 increased rapidity of the circulation. 



3. Ozone. — In addition to the foregoing 

 reasons for favoring a high altitude in the 

 cure of phthisis, we wish to consider, further, 

 the influence of elevation upon the ozone of 

 the atmosphere. 



The assertion is generally made, that, as " wo 

 ascend heights, the amount of the ozone rap- 

 idly- increases; " and yd there does not seem 

 to have been anj' direct experimentation on 

 this point. If there be more free ozone, it 

 may be due, not to any increased production 

 over that of lower levels, but rather to a di- 

 minished consumption. Further than this, the 



