CH. VII MICRO-SPECTROSCOPE AXD POLARISCOPE 169 



replaced by a single, less clearly defined band in about the same 

 position. The blood will also appear somewhat purple. Remove 

 the cork to admit fresh air then shake the vial vigorously and the 

 color will change to the bright red of fresh blood. Examine it 

 again with the spectroscope and the two bands will be visible. 

 After five or ten minutes another examination will show but a 

 single band. Incline the bottle so that a thin stratum may be 

 examined. Note that the stratum of liquid must be considerably 

 thicker to show the absorption band than was necessary to show 

 the two bands in the first fexperjment. Furthermore, while the 

 single band ma)' 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 oxy- 

 gen is present in the two banded spectrum but absent from the 

 single banded spectrum. When the bottle was shaken the hemo- 

 globin 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. 137). 



233. 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 a solution of blood in water of such a concen- 

 tration that the two oxy-hemoglobin bands run together, and then 

 adding three or four drops of a ^ per cent aqueous solution of per- 

 manganate of potash. Soon the bright red will change to a brown- 

 ish color, when it may be examined (Fig. 136). Instead of the 

 permanganate one may use hydrogen dioxide (H 2 O 2 ). 



>j 234. Carbon Monoxide Hemoglobin (CO-Hemoglobin). 



