THE BLOOD 



197 



Haemoglobin also combines with certain other gases. 

 Among these is Carbon monoxide. For this gas haemoglobin 

 has a greater affinity than for oxygen, so that when carbon 

 monoxide haemoglobin is once formed in the body, the 

 blood has little power of taking up oxygen, and the animal 

 dies. This gas is evolved freely in the fumes from burn- 

 ing charcoal, and the production of the compound in the 

 blood is the cause of death from inhaling such fumes in 



RED 



YELLOW. GREEN. 



BLUE. 



Carbon-monoxide ^ f 

 Hemoglobin . > f 



FIG. 101. Spectra of the more important Blood Pigments and their more important 

 derivatives. (The Spectrum of Acid Haematin is not identical with that of 

 Methsemoglobin). 



closed spaces. It is also found in the air of coal mines 

 after explosions. The carbon monoxide haemoglobin forms 

 crystals like oxy haemoglobin, and has a bright pinkish 

 red colour, without the yellow tinge of oxy haemoglobin. 

 Since after death it does not give up its carbon monoxide 

 and become changed to purple haemoglobin, the bodies of 

 those poisoned with the gas maintain the florid colour of 

 life. Its spectrum is very like that of oxyhaemoglobin, the 

 bands being slightly more to the blue end of the spectrum 

 (Fig. 101). 



