218 



THE BLOOD. 



owing to this fact, already mentioned, that when water is added to 

 the blood in sufficient quantity, the hemoglobine may be entirely ex- 

 tracted from the globules in a state of solution, leaving behind the 

 colorless substratum, much reduced in volume, but still remaining 

 undissolved for a considerable time. The exact physical condition of 

 the hemoglobine in the blood-globule and its mode of union with the 

 colorless substratum are not positively known. Preyer calculates that 

 the water of the blood-globule is quite insufficient in quantity to hold in 

 solution, by itself, the hemoglobine which is present ; and, according to 

 the same observer, it cannot exist in the blood-globules in a solid form, 

 since the crystals of hemoglobine are always doubly refracting, while 

 the fresh globules themselves are never so. So far as we can judge, the 

 two substances are united uniformly throughout the mass, in a condition 

 of thick or tenacious semi-fluidity ; but the hemoglobine is more easily 

 affected by various artificial dissolving agents, and by this means may be 

 extracted from the mass of the globule. 



Hemoglobine is remarkable for the avidity with which it absorbs 

 oxygen whenever, either as constituent of the blood-globules or in the 

 form of solution, it is brought in contact with this gas or with atmo- 

 spheric air. The brilliant red color presented by its solutions depends 

 upon the quantity of oxygen present ; for if this substance be exhausted 

 by means of the air-pump, the application of heat, or the displacing 

 action of an indifferent gas, the clear scarlet hue of the solution dis- 

 appears and is replaced by a dull red or purple color. 



Solutions of pure hemoglobine, as well as the blood-globules them- 

 selves, or diluted mixtures of blood and water, in the aerated condition, 

 exhibit a well-marked and peculiar spectrum. This spectrum is dis- 

 tinguished by the existence of two absorption bands between the lines 

 D and E, and situated, the one in the yellow, the other at the commence- 

 ment of the green. The first of these absorption bands is comparatively 



Pig. 82. 



BC D 



Red Or. Yel. Green Blue 



Violet 



SPECTRUM OF HEMOOLOBINE, in Aerated Blood. 



narrow, well defined, and dark, and is placed at about one-fifth the dis- 

 tance from D to E. The second is double the width of the first, but is 

 less dark, and not so well defined ; it occupies nearly the last half of 

 the space between D and E. Beyond the second band the light of the 



