THE BLOOD. 225 



monoxide takes the place of the molecule of oxygen combined 

 as oxy hemoglobin. This reaction is accompanied by a change 

 of color, not as marked, however, as the change from reduced 

 to oxyhemoglobin. The combination with carbon monoxide 

 is the reaction which takes place in cases of poisoning with 

 illuminating gas, which contains 10 to 25 per cent of the mon- 

 oxide. The addition of pure air does not displace the com- 

 bined gas except where a great excess is used. 



Ex. Lead a current of illuminating gas, best the so-called " water gas," 

 into 50 cc. of blood in a flask. Continue the passage of the gas until a 

 distinct cherry red color is produced. When the combination appears to 

 be complete treat a few cc. of the liquid with Stokes' solution, which fails 

 to effect a reduction. With portions of the mixture further tests should 

 be made to illustrate methods of differentiating between normal blood and 

 blood containing much monoxide. The differentiation in each case de- 

 pends on the greater stability of the monoxide hemoglobin with the re- 

 agent in question. 



Ex. Add some strong solution of sodium hydroxide to ordinary blood. 

 This gives a brownish green precipitate at first and then a red solution. 

 Treat blood saturated with carbon monoxide in the same manner. This 

 gives a red precipitate and finally a red solution. 



Ex. Dilute some of the monoxide blood with four volumes of water 

 and to the mixture add an equal volume of a 3 per cent tannic acid solu- 

 tion. The red color persists much longer than it would in the case of a 

 simple oxyhemoglobin solution, which should be tried for comparison. 



Ex. To about half a cubic centimeter of the monoxide blood add 20 

 cc. of water and 10 drops of strong yellow ammonium sulphide solution. 

 Shake thoroughly and then add enough dilute acetic acid to give a faint 

 acid reaction. A rose red color appears, while with normal blood decom- 

 position products are formed which have a dirty gray color. 



Ex. Mix i cc. of the monoxide blood with 5 cc. of basic lead acetate 

 solution and shake well. The mixture remains red, while with normal 

 blood under the same conditions a brown color results. 



Experiments have beer, carried out to determine what por- 

 tion of the hemoglobin must be combined \vith monoxide to 

 have death follow. It appears that if about half the pigment 

 in the blood is still unchanged recovery may be expected by 

 free use of air. The mere action of a great excess of air may 

 gradually displace the combined monoxide. The spectro- 

 scopic appearance of the monoxide hemoglobin will be re- 

 ferred to below. 

 16 



