212 



HAEMOGLOBIN. 



less and less, and the whole spectrum as far as G- appears beautifully 

 clear, except where the two absorption-bands are situated (Plate I., 

 Spectrum 2). If dilution be pushed still further, these disappear ; before 

 they vanish they appear as faint shadows across the limited region which 

 they occupy. The band a is said to disappear last. I find, however, that 

 whenever I can detect a I am able to detect a faint shadow in the 

 position of X 540-X 550. When the bands are just perceptible, there is 

 no obvious absorption of either the red or the violet end of the spectrum. 

 The two absorption-bands of oxyhaemoglobin are seen in greatest 

 perfection when a stratum 1 cm. thick of a solution containing 1 part 

 per 1000 of oxyhaemoglobin is examined; this corresponds to a solution 

 made by diluting from 1-2-14 parts of blood to 100. They are still 

 perceptible when the solution contains *L part oxyhtemoglobin in 100,000 

 parts of water (1 grm. in 10 litres). 



OXYILEMOGLOBIN. 



ABC 



ABC D 



FIG. 25. Graphic representation of the spectrum of oxyhaemoglobin and 

 htemoglobin. The numbers on the right are percentages. After 

 Kollett. 



The above figure illustrates a method of representing graphically 

 the variations in the spectrum of the blood-colouring matter, correspond- 

 ing to all concentrations (a stratum of 1 c.c. being examined). 1 



In these diagrams the position of the principal Frauenhofer lines 

 is shown ; the numbers on the right indicate percentages of the blood- 

 colouring matter. The shaded part of the diagram indicates absorp- 

 tion of light. By drawing lines parallel to the abscissae we at once 

 observe the character of the absorption spectrum which corresponds 

 to the concentration indicated at the right-hand side of each diagram. 

 Thus, by inspection of the left-hand diagram, we learn that solutions of 

 oxyhaemoglobin, containing more than 0*65 per cent., exhibit a single 

 broad absorption-band in the visible spectrum, owing to the fact that 

 the two absorption-bands and /3 have run together, and that the 

 green interspace between ~b and F is shown only by solutions of less 

 concentration than from O8 to 0*9 per cent. When the absorption of 

 this part of the spectrum is complete, only orange and red remain 

 unabsorbed. 



By placing the solution of oxyhaemoglobin in a wedge-shaped cell, 



1 A. Rollett, "PhysioloeiedesBlutes," Hermann's "Handbuch," Leipzig, 1880, Bd. iv. 

 Th. 1, S. 48. 



