October 3, 1912] 



NATURE 



151 



tributes to the maintenance of an adequate partial 

 pressure of oxygen. Haldane and Douglas say that 

 tlie percentage of red corpuscles and total quantity of 

 the hjemoglobin increases, and maintain 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 haemoglobin, this altera- 

 tion may not persist in shed blood ; for these products 

 mav disappear when the blood is exposed to air. 

 Owing to the combining power of haemoglobin 

 the respiratory exchange and metabolism of an animal 

 within wide limits are independent of the partial pres- 

 sure of oxygen. On the other hand, the process of 

 combustion is dependent not on the pressure, but on the 

 percentage of o.xygen. Thus the aeroplanist may be- 

 come 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 3000 feet is considerably 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 

 bv J. Harger, viz., to ventilate them with air contain- 

 ing 17 per cent, of oxv'gen.' There is little doubt that 

 all the great mine-explosions have been caused by the 

 enforcement of a high degree ot chemical purity of the 

 air. In the old days when ventilation was bad there 

 were no great dust explosions. Mr. \V. H. Chambers, 

 genera! 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 i\ per cent, of carbon dioxide. 

 .\ 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 ven- 

 tilation current that the percentage of oxygen is suffi- 

 cient for the spread of dust explosions along the intake 

 airways, with the disastrous results so frequently re- 

 corded. 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 the mines could be safely worked and 

 illuminated with electricity, and miners' nystagmus 

 prevented, for this is due to the dim light of the safety 

 lamp. The problem possibly may be solved by purify- 

 ing and cooling the return air, and mixing and cir- 

 culating this with a sufficiency of fresh air. 



Owing to the fact that the percentage of CO, is 

 the usual test of ventilation and that only a very few- 

 parts per 10,000 in excess of fresh air are permitted 

 by the English Factory Acts, it is generally supposed 

 that CO, is a poison, and that any considerable excess 

 has a deleterious effect on the human body. No sup- 

 position could be further from the truth. 



The percentage of CO, in the worst ventilated room 

 does not rise above o"5 per cent., or at the outside i 

 per cent. It is impossible that any excess of CO, 

 should enter into our bodies when we breathe such 

 air, for whatever the percentage of CO2 in the atmo- 

 sphere may be, that in the pulmonary air is kept 



^ Trans. Insr. of Minin:: KngTneer>. igi?. 



xo. 2240. VOL. go] 



constant at about 5 to 6 per cent, of an atmosphere— 

 by the action of the respiratory centre. It is the con- 

 centration of CO, which rules the respiratory centre, 

 and to such purpose as to keep the concentration both 

 in the lungs and in the blood uniform (Haldane) ; the 

 only result from breathing air containing o'5 to i per 

 cent, of CO, is an inappreciable increase m the ventila- 

 tion of the lungs. The very same thing happens when 

 wc take gentle exercise and produce more CO, in our 

 bodies. 



At each breath we rebreathe into our lungs the air 

 in the nose and large air-tubes (the dead-space air), 

 and about one-third of the air which is breathed in by 

 a man at rest in dead-space air. Thus, no man 

 breathes in pure outside air into his lungs. When a 

 child goes to sleep with its head partly buried under 

 the bedclothes, and in a cradle confined by curtains, he 

 rebreathes the expired air to a still greater extent, 

 and so with all animals that snuggle together for 

 warmth's sake. Not only the new-born babe sleeping 

 against its mother's breast, but pigs in a sty, young 

 rabbits, rats, and mice clustered together in their 

 nests, young chicks under the brooding hen, all alike 

 breathe a far higher percentage than that allowed by 

 the Factory Acts. 



To rebreathe one's ow-n breath is a natural and 

 inevitable performance, and to breathe some of the 

 air exhaled by another is the common lot of men 

 who, like animals, have to crowd together and hus- 

 band their heat in fighting the inclemency of the 

 weather. 



In the Albion Brewery we analysed on three 

 different davs the air of the room where the CO, 

 generated in the vats is compressed and bottled as 

 liquid carbonic acid. We found from o'i4 to 0^93 per 

 cent, of CO, in the atmosphere of that room. The 

 men who were filling the cylinders and turning the 

 taps on and off to allov.- escap? of air must often 

 breathe more than this. The men engaged in this 

 occupation worked twelve-hour shifts, having their 

 meals in the room. Some had followed the same 

 employment for eighteen years, and without detriment 

 to their health. It is only w-hen the higher concen- 

 trations of CO, are breathed, such as 3 to 4 per cent, 

 of an atmosphere, that the respiration is increased, so 

 that it is noticeable to the resting individual ; but per- 

 centages over I per cent, diminish the power to dp 

 muscular w'ork, for the excess of CO, produced by 

 the work adds its effect to that of the excess in the 

 air, and the difficulty of coordinating the breathing to 

 the work in hand is increased. 



Haldane and Priestley found that with a pressure 

 of 2 per cent, of an atmosphere of CO, in the inspired 

 air the pulmonary ventilation of a man at rest was 

 increased 50 per cent., w-ith 3 per cent, about 100 per 

 cent., with 4 per cent, about 200 per cent., with 5 per 

 cent, about 300 per cent., and with 6 per cent, about 

 500 per cent. With the last, panting is severe, while 

 with 3 per cent, it is unnoticed until muscular work 

 is done, when the panting is increased 100 per cent, 

 more than usual. With more than 6 per cent, the 

 distress is very great, and headache, flushing, and 

 sweating occur. 



Divers who work in diving dress and men who 

 work in compressed-air caissons constantly do heavy 

 and continuous labour in concentrations of CO. higher 

 than I per cent, of an atmosphere, and so long as the 

 CO, is kept below 2 to 3 per cent, they are capable 

 of carrving out efficient work. In the rase of workers 

 in compressed air it is imoortant to bear in mind that 

 the effect of the CO, on the breathing depends on the 

 partial pressure and not on the percentage of this 

 gas in the air breathed. 



Bv a series of observations made on rats confined 



