94 MEDICAL JURISPRUDENCE 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.