READJUSTMENTS OF REGULATION 45 
carbon monoxide poisoning. This gas (CO) is the 
poisonous constituent of ordinary lighting gas; and 
poisoning with it is extremely common in America 
on account of the high percentage of carbon monoxide 
in the carburetted water gas used extensively as a 
substitute for the old-fashioned coal gas still supplied 
in England. I discovered about twenty years ago that 
CO poisoning is also the cause of nearly all the deaths 
in great colliery explosions and fires, and a source of 
extreme danger to rescuers. 
Claude Bernard found that CO enters into combina- 
tion with haemoglobin, just as oxygen does, but forms 
a far more stable compound. In presence, therefore, 
of sufficient CO the oxygen-carrying power of the 
haemoglobin is suspended, and death must result from 
want of oxygen. It was supposed that CO has also a 
direct poisonous action on the nervous system. That 
this is not so I succeeded in showing by placing ani- 
mals in compressed oxygen before giving them CO. 
In the compressed oxygen sufficient oxygen goes into 
ordinary physical solution in the blood to enable 
the animal to dispense with oxyhaemoglobin as an 
oxygen carrier; and the animal remains unharmed 
although its blood and tissues are saturated with CO. 
Animals which do not employ oxygen haemoglobin as 
an oxygen carrier live for weeks quite comfortably in 
an artificial air composed of 80 per cent of CO and 
20 per cent of oxygen. CO is not oxidised in the 
living body, and apart from its one fatal property of 
combining with haemoglobin it is a physiologically 
indifferent gas. - 
