THE BLOOD. 



85 



intense, but narrower than the other, which lies in the green near to the 

 left 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 unabsorbed, and part of 

 the red; on still further increase of the 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 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 be- 

 come purple in a similar manner. 



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



FIG. 79. 



FIG. 80. 



FIG. 79.-Oxy-h8emoglobin crystals tetrahedral, from blood of the guinea-pig. 

 FIG. 80. Hexagonal oxy-haemoglobin crystals, from blood of squirrel. On these hexagonal 

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



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

 or ammonium sulphide is the most convenient. 



With the spectroscope, a solution of deoxidized or reduced haemo- 

 globin is found to give an entirely different appearance from that of 

 oxidized haemoglobin. 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 same time less of the blue end of the spectrum is ab- 

 sorbed. Even in strong solutions this latter appearance is found, 

 thereby differing from the strong solution of oxidized haemoglobin 



1 Stokes' 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. N H 4 H S. 



