92 A TEXTBOOK OF PHYSIOLOGY 







The presence of CO in coal-gas and in after-damp in mines is a 

 frequent cause of death. CO has about 150 times as great an affinity 

 for Hb as O , and thus it comes about that, if a man breathes long 

 enough an atmosphere containing 0-1 percent. CO, half the oxygen will 

 be displaced from his blood. The haemoglobin of the blood becomes 

 combined to form COHb, insufficient oxygen is now carried to the 

 tissues, and death from oxygen want ensues. It is therefore dangerous 

 to breathe an atmosphere containing more than 0-05 per cent. CO is 

 without colour or smell, and its presence cannot be sensed. The want 

 of oxygen gives little warning, and a man breathing CO may lose 

 consciousness unwitting of his danger. A small vertebrate, such as 

 a bird or mouse, is affected much sooner than a man, and it is a wise 

 precaution to send a cage bird with an exploring party into a mine 

 where " after-damp " exists. Ordinary illuminating gas contains 

 about 5 per cent, of carbon monoxide, and water-gas, used in some 

 towns, as much as 30 to 40 per cent. CO poisoning in such towns 

 has accounted for even 1 per cent, of all the deaths. Seventy-five 

 per cent, saturation of the haemoglobin with CO causes dizziness and 

 palpitation on exertion; the heart fails to keep up the extra circula- 

 tion required then. Brain-power is greatly diminished although the 

 subjects do not know it. In deaths from house on fire the people 

 are as a rule rendered unconscious by CO poisoning before they are 

 burnt. The bodies of men killed by CO poisoning have a pink colour, 

 due to the COHb formed. 



Nitroxyhsemoglobin (NOHb) also has a spectrum resembling the 

 above, but the two bands, although in approximately the same posi- 

 tion, are not by any means so clear-cut; the shading appears " woolly." 

 NOHb is not reduced by ammonium sulphide. It is prepared by 

 adding a solution of ammonia to the blood, and then passing nitric 

 oxide gas through the solution. It is formed in the blood by the action 

 of the nitrites e.g., amyl nitrite or such bodies as nitro-benzol. 

 Methsemoglobin is first formed, and afterwards nitroxyhsemoglobin. 



For cases of partial poisoning by carbon monoxide or nitrites the 

 correct treatment is to place the patient in an atmosphere of oxygen, 

 preferably under pressure, so that the Hb which is uncombined may 

 have an ample supply of oxygen to draw upon, and more oxygen may 

 become dissolved in the plasma of. the blood owing to its increased 

 partial pressure. At a pressure of oxygen of two atmospheres about 

 2-5 per cent, of oxygen is dissolved in the plasma, and this is enough 

 to maintain life in the presence of any percentage of CO. A mouse 

 poisoned by CO, and rendered moribund, revives in two atmospheres 

 of oxygen, and tumbles over again when the pressure is lowered to 

 atmospheric pressure. The resuscitation and swooning of the mouse 

 may be repeated. 



NOHb is even more stable than COHb. It can be distinguished 

 from COHb by giving a bright red coagulum on boiling, whereas 

 COHb gives a brownish one. The difference in colour is approximately 

 that between the outer red ring of salt beef and the inner brown zone. 

 In this case the haemoglobin hi the muscle has formed NOHb owing 



