i el eee 
PRESIDENTIAL ADDRESS. 631 
the hemoglobin of the venous blood into oxyhemoglobin there can arise no lack 
of oxygen. 
At sea-level the pressure of oxygen in the pulmonary alveolar air is about 
100 mm. Hg. Exposed to only half this pressure the hemoglobin is more than 
80 per cent. saturated with oxygen. 
In noted health-resorts of the Swiss mountains the barometer stands at 
such a height that the concentration of oxygen is far less than in the more 
ventilated room. On the high plateau of the Andes there are great cities : Potosi 
with a hundred thousand inhabitants is at 4,165 metres, and the partial pressure 
of oxygen there is about 13 per cent. of an atmosphere in place of 21 per cent. 
at sea-level; railways and mines have been worked up to altitudes of 14,000 to 
15,000 feet. At Potosi girls dance half the night, and toreadors display their 
skill in the ring. On the slopes of the Himalayas shepherds take their flocks 
to altitudes of 18,000 feet. No disturbance is felt by the inhabitants or those 
-who reach these great altitudes slowly and by easy stages. The only disability 
to a normal man is diminished power for severe exertion, but a greater risk arises 
from want of oxygen to cases of heart disease, pneumonia, and in chloroform 
anesthesia at these high altitudes. The newcomer who is carried by the railway 
in a few hours to the top of Pike’s Peak or the Andes may suffer severely from 
mountain sickness, especially on exertion, and the cause of this is want of oxygen. 
Acclimatisation is brought about in a few days’ time. The pulmonary ventilation 
increases, the bronchial tubes dilate, the circulation becomes more rapid. The 
increased pulmonary ventilation lowers the partial pressure of carbon dioxide in 
the blood and pulmonary air, and this contributes to the maintenance of an 
‘adequate partial pressure of oxygen. Haldane and Douglas say that the percen- 
tage of red corpuscles and total quantity of the hemoglobin increases, and main- 
tain that the oxygen is actively secreted by the lung into the blood, but the CO 
method by which their determinations have been made has not met with 
unqualified acceptance. If waste products, which arise from oxygen want, alter 
the combining power of hemoglobin, this alteration may not persist in shed 
blood; for these products may disappear when the blood is exposed to air. 
Owing to the combining power of hemoglobin the respiratory exchange and 
metabolism of an animal within wide limits is independent of the partial pressure 
of oxygen. On the other hand, the process of combustion is dependent not on 
the pressure but on the percentage of oxygen. Thus the aeroplanist may become 
seized with altitude sickness from oxygen want, while his gas engine continues 
to carry him to loftier heights. 
The partial pressure of oxygen in a mine at a depth of 3,000 feet is consider- 
ably higher than at sea-level, and if the percentage is reduced to 17, while the 
firing of fire-damp and coal dust is impossible, there need be in the alveolar air 
of the lungs no lower pressure of oxygen than at sea-level. Thus the simplest 
method of preventing explosions in coal mines is that proposed by J. Harger, 
viz., to ventilate them with air containing 17 per cent. of oxygen.’ There is little 
doubt that all the great minc-explosions have been caused by the enforcement 
-of a high degree of chemical purity of the air. In the old days when ventilation 
was bad there were no great dust explosions. Mr. W. H. Chambers, general 
manager of the Cadeby mine, where the recent disastrous explosion occurred, 
with the authority of his great and long practical experience of fiery mines, 
told me that the spontaneous combustion of coal and the danger of explosion can 
be wholly met by adequate diminution in ventilation. The fires can be choked 
out while the miners can still breathe and work. The Coal Mines Regulation 
‘Act enforces that a place shall not be in a fit state for working or passing therein, 
if the air contains either less than 19 per cent. of oxygen, or more than 14 per 
-eent. of carbon dioxide. A mine liable to spontaneous combustion of coal may be 
exempted from this regulation by order of the Secretary of State. 
The regulations impel the provision of such a ventilation current that the 
percentage of oxygen is sufficient for the spread of dust explosions along the 
intake airways, with the disastrous results so frequently recorded. If the mine 
were ventilated with air containing 17 per cent. of oxygen in sufficient volume 
to keep the miners cool and fresh, not only would explosions be prevented but 
1 Trans, Inst. of Mining Engineers, 1912. 
