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Fig. 25.—Microphotograph of Hsemochromogen Crystals X 500.
(Khan Bahadur Dr. N. J. Vazifdar.)

verted into methaemoglobin owing to exposure to air and light. Its spectrum
consists of four absorption bands, one band in the re-cUorange between the
lines, C and D, at wave length 634, two thjn&£x and fainter bands between
the lines, D and E, in the same position as those of oxyKsemoglobin, and a
fourth band in the green between the lines, E and R, at wave length 500,
but it is very seldom denned and seen (see Plate I).

^In India, blood stains are liable to putrefy rapidly, if kept damp. If
they'are kept dry, they become insoluble and resist the action of the ordinary
solvents. Either of these changes may render recognition of the stains diffi-
cult and sometimes impossible. Hence Hankin 19 has elaborated a method by
which the stains may show the absorption bands of haemochromogen or
reduced haematin, even though the blood pigment its apparently insoluble.
The spectrum of this compound is characterized by the presence of two
absorption bands. The first is a very sharp and dark band midway between
the lines, D and E, and lying at wave lengths 568-550 ; the second is a broader
but paler band, which commences on the left of the line, E, at wave lengths
537-521 and gradually fades away beyond this line. It may be noted that
an alkaline solution of haBmochromogen absorbs oxygen from air and readily
changes to haematin (alkaline) which gives an altogether different spectrum.
The following is the technique for obtaining the spectrum, of
hsemochromogen : —

A small portion of the suspected stain is placed on a glass slide and
moistened with ammonium sulphide as a reducing agent. It is then focussed
under the microscope. The eye piece is removed and an ordinary direct
vision spectroscope with the wave length scale is inserted into the micro-
scope-tube to serve the purpose of a microspectroscope. If the stain is due
to blood, the two absorption bands of haemochromogen will be visible. The

19.   Brit. Med. Jour., Nov. 10, 1906, p. 1261.