HESPIRATION 293 



is burned with an insufficient supply of oxygen gas, as 

 when fresh coal is placed upon the top of a furnace fire. 

 It does not arise in the living body and its interest in this 

 connection comes from the danger of inhaling it. We 

 may be subjected to its effects when it has reached us 

 from fires or when illuminating gas escapes into our 

 rooms. The common form known as "water gas" con- 

 tains it in great quantity. It is very poisonous and 

 for a simple reason: it deprives the blood of its oxygen- 

 carrying capacity. 



Carbon monoxid does this by replacing oxygen in the 

 oxyhemoglobin molecule. The unnatural compound 

 formed is a stable one and circulates with little tendency 

 to release the carbon monoxid which is locked in it. 

 Just so far as the corpuscles become engaged in carry- 

 ing this useless gas they are incapacitated for their 

 essential service. If the substitution becomes extensive 

 enough the lack of oxygen becomes fatal, the heart and 

 the nervous system failing for want of it much as though 

 the victim were bleeding to death. The blood, when 

 saturated with carbon monoxid, has a light color de- 

 scribed as cherry red and does not darken on standing 

 as normal blood does. 



Breathing Pure Oxygen. The impression is common 

 that the experience of breathing pure oxygen is a highly 

 exhilarating one. This is not really the case unless an 

 element of suggestion secures the anticipated result. 

 If a man does not know that he has been given the oxygen 

 to breathe he is not likely to report that the experience 

 is at all peculiar. Nevertheless oxygen has often seemed 

 to be of the utmost value in critical pulmonary disease. 

 We must try to reconcile the negative reaction of one 

 who breathes it in health and the marked relief of the 

 pneumonia patient. A simple statement may explain 

 the difference: oxygen does not alter the composition of 

 normal blood in a way that will much affect the organism 

 but it is potent to restore to the standard blood which 

 may have fallen below in illness. 



