120 



THE BLOOD 



The forms of hemoglobin crystals, as will be seen from figures 119 and 

 120, differ greatly. Hemoglobin crystals are soluble in water. Both the 

 crystals themselves and also their solutions have the characteristic color of 

 arterial blood. 



A dilute solution of oxyhemoglobin gives a characteristic appearance 

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

 lines D, which is the sodium band in the yellow, and E, see the frontispiece, 

 one in the yellow, with its middle line some little way to the right of D. This 

 band is very 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. Both the red and the blue ends of the spectrum be- 

 come encroached upon until the bands coalesce to form one very broad band 

 when only a slight amount of the green and part of the red remain unab- 



FIG. 121. Hexagonal Oxyhemoglobin Crystals, from Blood of Squirrel. On these hex- 

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



sorbed. Any further increase of strength leads to complete absorption of 

 the spectrum. 



If crystals of hemoglobin are exposed to an atmosphere of oxygen they 

 take up oxygen and form oxyhemoglobin, each gram of the pigment fixing 

 a definite amount of oxygen, see chapter on Respiration. When subjected 

 to a mercurial air pump the oxygen is given off, and the crystals become 

 of a purple color. A solution of the oxyhemoglobin in the blood-corpuscles 

 may be made to give up oxygen, and to change color in a similar manner. 

 One gram of oxyhemoglobin liberates 1.59 c.c. oxygen, or according to Hiif- 

 ner's later determinations, 1.34 c.c. 



This change may be also effected by passing through the solution of 

 blood or of oxyhemoglobin, hydrogen or nitrogen gas, or by the action of 



