258 LECTURES TO SCIENCE TEACHEES. 



with oxygen termed oxy-haemoglobin which is not very 

 stable. It takes oxygen up from the lungs, conveys it to 

 the tissues, and there gives it off ; but it also forms com- 

 binations with other gases besides oxygen, and this is a point 

 of very great practical importance. With carbonic oxide, 

 the gas which is given off from charcoal stoves, it forms 

 a combination very much resembling oxy- haemoglobin in 

 colour, but differing from it in this respect, that whereas oxy- 

 hsemoglobin is readily reduced, carbonic-oxide-haemoglobin 

 is quite stable, and not easily broken up. In consequence of 

 this property, if I were to take some blood saturated with 

 carbonic oxide, which resembles ordinary arterial blood 

 in appearance, except in being a little brighter, and shake 

 it up with some of Stokes's fluid, I should get no change 

 in it. The important point about this fact is, that when 

 persons are confined in small rooms with charcoal stoves 

 the haemoglobin in their blood forms, with the carbonic 

 oxide, this compound, which is no longer of any use for 

 respiration ; the carbonic oxide has displaced the oxygen, 

 and there is no oxygen carried from the lungs to the tissues, 

 so that the respiration of the tissues cannot go on. When 

 persons are in this condition it is of no use to keep up 

 artificial respiration, as would be the case if the person 

 had fallen into a brewer's vat; the only remedy is to 

 introduce some fresh blood. This was done in a case which 

 occurred at Berlin some time ago. A person was found 

 lying in a state of unconsciousness in a room with a char- 

 coal stove. The doctor who was called to attend him 

 found that he was so far gone that artificial respiration 

 would be of no use. From previous experiments he 

 knew exactly the condition of the blood, and at once 

 proceeded to transfuse healthy blood into the patient's 

 veins. The blood thus introduced was carried to the heart 

 and lungs, took up the oxygen, thence circulated to all 

 parts of the body, and the man recovered perfectly. If it 

 had not been for the previous experiments which proved 

 that haemoglobin when brought in contact with carbonic 

 oxide forms this peculiar compound, that man's life would 

 not have been saved. This affords a good example of the 

 way in which experiments made purely from scientific 

 curiosity and without any practical end in view afterwards 

 become of the greatest practical use. 



