VISIBLE SPECTRUM OF OXYHEMOGLOBIN. 211 
The spectrum as seen with solutions of varying concentration.— 
When well-arterialised defibrinated blood (containing on an average 
from 1 2 to 14 per cent, of oxyhsemoglobin) is diluted with nine times 
Its volume of distilled water, and a stratum 1 cm. thick is brought before 
the slit of the spectroscope, it will be found that the whole of the 
spectrum is absorbed, with the exception of the red end, or rather of 
those rays having a wave Length greater than about GOO millionths of 
a millimetre (/. 000). 
[f, now, the blood solution be gradually diluted, a point is reached 
at which the spectrum is (proceeding from the red end) clear up to 1) 
(>. 598), and a strip of greeD is visible between b and F (>. 518-3-a486\I ). 
Between 1) and b the absorption is intense (see Plate I., Spectrum 4), 
and beyond F no trace of Light appears. On diluting still further, that 
Fig. 23. — The haeinatinometer. 
Fig. 24. — The hsematoscope. 
which appeared as a single wide absorption-band between D and b, and 
afterwards as the solution was progressively diluted between D and E, 
is seen to resolve itself into two distinct absorption-hands, separated by 
a green interspace ; the violet end of the spectrum is still powerfully 
absorbed (Plate I., Spectrum 3). 
Of the two absorption-bands just referred to, the one next to D is 
narrower than its fellow; it has more sharply denned borders, and to the 
eye appears marc intense; its centre corresponds to X 579, and we may 
conveniently distinguish it as the absorption-band a in the spectrum of 
oxyhsemoglobin. 
The second of these absorption-bands, i.e. the one next to E, which 
we shall designate the band /3, is broader, has less sharply-defined edges, 
and its centre corresponds approximately to X 553 - 8. Between the two 
hands is a green interspace. 
On diluting the solution more and more largely, and continuing to 
examine a stratum 1 cm. thick, the absorption of the violet end becomes 
