46 ORGANISM AND ENVIRONMENT 



In CO poisoning there is usually only a small per- 

 centage of CO in the air, and as the haemoglobin of 

 the blood has a large capacity for CO it takes a con- 

 siderable time for enough CO to accumulate in the 

 blood to cause dangerous symptoms. These symp- 

 toms, however,, come on in exactly the same insidious 

 manner as those from oxygen want arising in any 

 other way. The headache, nausea, etc., of CO poison- 

 ing are the same as those of mountain sickness, and 

 the more remote nervous, cardiac, and other after- 

 symptoms of CO poisoning or serious oxygen want 

 produced in any other way are due to damage result- 

 ing from oxygen want, and to no other cause. The 

 oxygen want produces not merely temporary func- 

 tional effects, but structural changes in the cells of 

 nervous and other tissues. 



As CO in small but extremely dangerous propor- 

 tions in air cannot be detected by smell or by a lamp, 

 I introduced, as a test for it, the use of a small warm- 

 blooded animal, such as a mouse or canary. A small 

 animal has an enormously greater respiratory ex- 

 change and circulation rate than a man; and in con- 

 sequence its blood becomes saturated with CO far 

 more quickly. By watching the animal a miner can 

 tell in good time whether he is in a dangerous atmos- 

 phere, though in the long run the animal is not more 

 sensitive to CO than the man. The provision of small 

 animals for testing purposes at mines in Great Britain 

 was made obligatory by recent legislation. 



Yandell Henderson discovered that after excessive 

 artificial respiration on animals the breathing does 



