330 RESPIRATION 



chlorine, discharged into the air in a good breeze as "drift gas" 

 from cylinders of liquefied gas. The liquefied gas quickly evapo- 

 rated, thus cooling a large body of air which rolled along the 

 ground, producing at the same time a mist if the air was nearly 

 saturated, and passing downwards into every trench. From ac- 

 counts given by officers and men at the time, I estimated that 

 along the lines attacked there was usually about .01 per cent of 

 chlorine in the air; but of course the percentage would vary. At 

 about this and higher concentrations, chlorine has an immediate 

 and severe irritant effect on the air passages, and a less severe 

 action on the eyes. Bronchitis follows if the exposure lasts for 

 more than a very short time, and some time later symptoms of 

 oedema of the lungs appear, owing to the action of the gas on the 

 alveolar walls. The symptoms are then similar to those which 

 follow exposure to nitrous fumes. The men suffering from this 

 condition were deeply cyanosed, with superficial veins about the 

 neck prominent, greatly increased depth and rate of breathing, 

 and a frequent, but usually fairly strong pulse. Intelligence was 

 clouded, but the distress seemed very great. 



On testing a drop of blood by diluting it to a yellow color, 

 saturating with coal gas and comparing the pink tint thus pro- 

 duced with the tint of normal blood similarly diluted, it was evi- 

 dent that there was no decomposition of the haemoglobin. The 

 cyanosis was therefore due to imperfect saturation of the blood 

 with oxygen. That the imperfect saturation was due, not to slow- 

 ing of the circulation, but to imperfect saturation in the lungs, 

 was shown at once by the effect of giving oxygen. This abolished 

 the cyanosis, cleared up the clouded intelligence, but had no great 

 effect on the breathing. On post mortem examination of fatal 

 cases it was found that the lungs were voluminous and greatly 

 congested. Large quantities of albuminous liquid could be 

 squeezed out through the cut bronchi, and there was much em- 

 physema. 



The interpretation of the more dangerous symptoms seems 

 fairly clear. The cyanosis was due to the fact that the blood in 

 passing through the lungs was imperfectly oxygenated, owing 

 mainly to swelling and exudation, which hindered the diffusion 

 of oxygen inwards to the blood. On raising the alveolar oxygen 

 pressure when oxygen was given, the diffusion became much 

 faster and the blood was properly oxygenated. The hyperpnoea 

 remained, however, and was probably attributable to the fact 

 that though much air was entering the lungs, a great deal of it 



