It is shown in Fig. 1 that there is no perceptible difference in the visible
region between the absorption spectra obtained from hemolyzed human
blood and pure calf hemoglobin. It may therefore be concluded that
other blood constituents make a negligible contribution to the light absorption
of hemolyzed blood in this region. The results also bear out the
previous findings of Drabkin and Austin (11) and others with regard to the
spectroscopic identity of the hemoglobins of various mammalian species.
In the infra-red region, where the absorption of hemoglobin is much less
intense, whole blood absorbs appreciably more than does pure hemoglobin
(see Fig. 2). This difference may be attributed to the absorption of light
by other blood constituents and to scattering of light by suspended material
such as lipids and cell fragments. At the high dilutions used for the visible
measurements the contribution of these materials is negligible. It is noteworthy
that no special precautions were taken in the collection of the blood
samples. The individuals were not required to fast before the venipunctures
were made, the only limitation being that no samples were taken for
several hours after lunch.