THE EFFECTS OF EXCESS OF CARBON DIOXIDE 305 



with slight dyspnoea or air-hunger, consciousness may be lost, followed 

 by paralysis, or in some cases the paralysis of the muscles, particularly 

 those of the limbs, may precede the loss of consciousness. Thus, in 

 a balloon ascent, at 29,000 feet, Coxwell, although suddenly finding 

 himself paralyzed in his limbs, was able to pull with his teeth the 

 safety-valve rope of the balloon, and to save himself and Glaisher. 

 In the case of the ascent of Croce-Spinelli, Sivel, and Tissandier, the 

 aeronauts were all paralyzed suddenly before they could breathe 

 from the oxygen bags with which they had provided themselves. 

 Similar symptoms follow gradual poisoning by carbon monoxide or 

 coal-gas. Miners display the same lack of judgment when affected 

 by carbon monoxide. - 



Normal 

 respiration 



1st stage 

 (prolonged 

 expiration) 



2nd stage 

 (expiratory 

 convulsions) 



3rd stage 

 (exhaustion 



Time in seconds 



FIG. 171. ASPHYXIA TRACING : RABBIT. (Waller.) 

 The line falls with inspiration, rises with expiration. 



In carbon monoxide poisoning, the lack of oxygen is brought about 

 by the decreased oxygen-carrying capacity of the blood, due to the 

 formation of COHb. The symptoms begin to sho.v themselves when 

 the blood is one-fourth saturated. With 50 per cent, saturation, thf 

 mental symptoms become marked, and the slightest exertion is danger- 

 ous, since it may bring on convulsions and death. It is dangerous to 

 breathe air containing as little as 0-05 per cent. CO, for the affinity 

 of CO for Hb is about 150 times that of 2 . There is 5 to 6 per cent. 

 CO in coal-gas, as much as 30 per cent, in water-gas, 3 per cent, or 

 more in after-damp after explosions in mines. CO occurs in con- 



20 



