CH. VIII] USING THE MICRO-SPECTROSCOPE 261 



experiment. Furthermore, while the single band may be made quite 

 black on thickening the stratum, it will not separate into two bands 

 with a thinner stratum. In this experiment it is very instructive 

 to have the watch glass of arterial blood under the microscope and 

 the vial of blood to which has been added the ammonium sulphide 

 in position for a comparison spectrum. 



The two-banded spectrum is that of oxy-hemoglobin, or arterial 

 blood; the single-banded spectrum of hemoglobin (sometimes called 

 reduced hemoglobin) or venous blood, that is, the respiratory oxygen 

 is present in the two-banded spectrum but absent from the single- 

 banded spectrum. When the bottle was shaken the hemoglobin 

 took up oxygen from the air and became oxy-hemoglobin, as occurs in 

 the lungs, but soon the ammonium sulphide took away the respiratory 

 oxygen, thus reducing the oxy-hemoglobin to hemoglobin. This 

 may be repeated many times (fig. 149). 



414. Met-hemoglobin. The absorption spectrum of met- 

 hemoglobin is characterized by a considerable darkening of the blue 

 end of the spectrum and of four absorption bands, one in the red 

 near the line C and two between D and E, nearly in the place of the 

 two bands of oxy-hemoglobin; finally there is a somewhat faint, 

 wide band near F. Such a met-hemoglobin spectrum is best obtained 

 by making the solution of blood in water of such a concentration that 

 the two oxy-hemoglobin bands run together, and then adding three 

 or four drops of a 0.1% aqueous solution of permanganate of potash. 

 Soon the bright red will change to a brownish color, when it may be 

 examined (fig. 148). Instead of the permanganate one may use 

 hydrogen dioxide (H 2 O 2 ). 



415. Carbon monoxide hemoglobin (CO-hemoglobin). To 

 obtain this, kill an animal in illuminating gas, or one may allow 

 illuminating gas to bubble through some blood already taken from the 

 body. The gas should bubble through a minute or two. The oxy- 

 gen will be displaced by carbon monoxide. This forms quite a stable 

 compound with hemoglobin, and is of a bright cherry-red color. Its 

 spectrum is nearly like that of oxy-hemoglobin, but the bands are 

 farther toward the blue. Add several drops of ammonium sulphide 

 and allow the blood to stand some time. No reduction will take 



