l6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 60 



miners' nystagmus be prevented, for this is due to the dim light of 

 the safety-lamp. The comfort and the working power of the miners 

 would be greatly augmented in a well-lighted mine. To show how 

 little the proposed diminution in the oxygen percentage affects the 

 men, Harger cites a»report of Cadman and Whalley concerning a 

 place where there was a quantity of black damp given off, and where 

 " a light would not burn I foot 6 inches from the floor, or in the 

 waste, but the men had no fault to find with the atmosphere." The 

 foreman said it was " better than usual." 



Analyses of samples taken (i) at the floor, and (2) at the coal 

 face showed : 



The problem perhaps may be solved by purifying and cooling fur- 

 nace air, and mixing and circulating this with a sufficiency of fresh air. 



All the experimental evidence which we detail later goes to show 

 that it is only when the partial pressure of oxygen is lowered very 

 considerably that signs of oxygen want arise. The athlete suffers 

 from oxygen want in the performance of any rapidly executed and 

 strenuous effort because he uses up oxygen in his muscles more 

 rapidly than it can be supplied by the respiration and circulation. 

 The rapid contraction of the muscles impedes the circulation of blood 

 through the muscles. The blood can flow through them only during 

 the relaxations, not during the contractions. Douglas and Haldane 

 have found that a man doing the hard exercise of pushing a motor- 

 cycle up a steep hill may use up 3,000 cc. of oxygen per minute against 

 300 cc. when resting. The heart called upon to circulate blood ten 

 times as fast — a strenuous effort — may suffer from want of oxygen, 

 because the circulation of blood through the coronary vessels is 

 impeded by the contraction of the heart muscle during the height of 

 systole, and the total period spent in systole is increased when the 

 heart beats quickly. To start with the lungs full of pure oxygen 

 benefits the athelete ; so, too, the breathing of oxygen helps him when 

 cycling and exhausted, or in the intervals of boxing. The strength 

 of the pulse and the fulness of the artery are increased and the f re- 

 quency of the heart diminished thereby. The athlete in these con- 

 ditions is like the mountain-sick person. So, too, the pneumonic 

 patient is benefited by oxygen-inhalation. Apart from the influence 

 of high concentrations of oxygen in conditions of extraordinary 

 exertion or in disease, the evidence shows that a diminution of 



