yz HAND-BOOK OF PHYSIOLOGY. 



A dilute solution of haemoglobin gives a characteristic appearance with 

 the spectroscope. Two absorption bands are seen between the solar lines 

 D and E (see Plate), one toward the red, with its middle line some little 

 way to the blue side of D, is very intense, but narrower than the other, 

 which lies near to the red side of E. Each band is darkest in the middle 

 and fades away at the sides. As the strength of the solution increases the 

 bands become broader and deeper, and both the red and the blue ends of 

 the spectrum become encroached upon until the bands coalesce to form 

 one very broad band, and only a slight amount of the green remains un- 

 absolved, and part of the red, and on further increase of strength the 

 former disappears. 



If the crystals of oxy-haemoglobin be subjected to a mercurial air-pump 

 they give off a definite amount of oxygen (1 gramme giving off 1-59 



FIG. 82. 



FIG. 82. Oxy-hsemoglobin crystals tetrahedral, from blood of the guinea-pig. 

 FIG. 83. Hexagonal oxy-heemoglobin crystals, from blood of squirrel. On these hexagonal 

 plates, prismatic crystals, grouped in a stellate manner, not unfrequently occur (after Funke). 



c.cm. of oxygen), and they become of a purple color; and a solution of oxy- 

 haemoglobin may be made to give up oxygen and to become purple in a 

 similar manner. 



This change may be also effected by passing through it hydrogen or 

 nitrogen gas, or by the action of reducing agents, of which Stokes's fluid 1 

 is the most convenient. 



With the spectroscope a solution of deoxidized haemoglobin is found 

 to give an entirely different appearance from that of oxidized haemoglo- 

 bin. Instead of the two bands at D and E we find a single broader but 

 fainter band occupying a position midway between the two, and at the 



1 Stokes* 's Fluid consists of a solution of ferrous sulphate, to which ammonia has 

 been added and sufficient tartaric acid to prevent precipitation. Another reducing 

 agent is a solution of stannous chloride, treated in a way similar to the ferrous sulphate, 

 and a third reagent of like nature is an aqueous solution of ammonium sulphide. 



