2 1 2 HAL MO GL OB IN. 
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 ,\ 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 oxyhemoglobin are seen in greatest 
perfection when a stratum 1 cm. thick of a solution containing 1 part 
per 1000 of oxyhemoglobin is examined; this corresponds to a solution 
mule by diluting from 1 -2-1*4 parts of blood to 100. They are still 
perceptible when the solution contains 1 part oxyhemoglobin in 100,000 
parts of water (1 grm. in 10 litres). 
Oxyhemoglobin - . 
H.EMOGLOB1S. 
Fig. 25. — Graphic representation of the spectrum of oxyhemoglobin ami 
haemoglobin. 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 
oxyhemoglobin, 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 a and IS have run together, and that the 
green interspace between b and F is shown only by solutions of less 
concentration than from - 8 to 0*9 per cent. When the absorption of 
this part of the spectrum is complete, only orange and red remain 
unabsolved. 
By placing the solution of oxyhemoglobin in a wedge-shaped cell, 
1 A. Rollett, "PhysiologiedesBlutes," Hermann's "Handbuch," Leipzig, 1880, Bd. iv. 
Th. 1, S. 48. 
