IDENTIFICATION OF BLOOD. 6l 



substance is soluble, with exclusion of oxygen, in dilute alkalies, with the formation 

 of a cherry-red color, and exhibits two absorption-bands, namely, one between 

 D and E, and another and narrower between E and b (Fig. 15, 7). 



Hemochromogen can be prepared in crystalline form by mixing upon a glass 

 slide one drop of defibrinated blood with one drop of pyridin and covering the 

 whole. The preparation exhibits the absorption-bands and at times also small 

 crystals arranged in the form of stars or sheaves. In the bloody extract of 

 spirit-preparations no longer fresh putrefaction often produces the beautiful red 

 hemochromogen in alkaline solution. 



Dilute acids in alcoholic solution withdraw the iron from the hemochromogen 

 and there thus results hematoporphyrin C 16 H 18 N 2 O 3 , which is isomeric with 

 bilirubin, and is permanent in the air. This can also be prepared from hematin 

 by means of strong sulphuric acid. It exhibits in acid solution a small absorption- 

 band in the orange and a wider band in the yellowish-green (Fig. 16, i). The 

 spectrum of the same substance in alkaline solutions is shown in Fig. 16, 2. 



Hematin occurs in solution as 



(A) Hematin in acid solution. If acetic acid be added to a solution of hemo- 

 globin the latter becomes mahogany-brown in color, as hematin in acid solution 

 develops and is recognized by four absorption-bands in the yellow and the green 

 (Fig. 15, 5)- 



(B) If this solution be over-saturated with ammonia hematin in alkaline 

 solution develops, exhibiting an absorption-band at the junction between the red 

 and the yellow (Fig. 15, 6). 



(C) Addition of reducing agents causes disappearance of this band and pro- 

 duces tw r o wide bands in the yellow, due to the reduced hematin thus formed 

 (Fig. 15, 7), and which, according to Hoppe-Seyler, is identical with the hemo- 

 chromogen in alkaline solution. 



Hematin is prepared in substance by precipitation from a solution of hemin 

 in a weak alkali by addition of a dilute acid. 



Hemoglobin is transformed into green sulphur-methemoglobin by hydrogen 

 sulphid. This substance also causes the green coloration of putrid portions of 

 the cadaver. 



Hematin when reduced in alkaline solution with tin and hydrochloric 

 acid yields urobilin. The latter results likewise through the action of 

 hydrogen dioxid on acid hematin. 



Urobilin is occasionally found in cysts, exudates, and transudates. It forms 

 likewise in sterile blood kept at the temperature of the body. 



HEMIN (HEMATIN CHLORID); IDENTIFICATION OF BLOOD BY 

 MEANS OF THE HEMIN-TEST. 



Teichmann prepared in 1853 from the anhydrid of hematin crystals 

 that Hoppe-Seyler recognized as hematin chlorid C 3 2H 30 N 4 O 3 FeHCl. 

 As these may be obtained in characteristic form even from traces of 

 blood they play an important role in forensic medicine. The demonstra- 

 tion of their presence depends upon the fact that the hemoglobin dried 

 and heated with an excess of water-free acetic acid so-called glacial 

 acetic acid, which must burn on a glass rod held in the flame and 

 addition of sodium chlorid yields hemin-crystals (Figs. 17 and 18). 

 These appear in the form of small rhombic plates, columns, or rods, 

 although they probably belong to the monoclinic system. Not 

 rarely they take the form of hemp-seeds or shuttles or paragraph- 

 signs. At times some lie crossed or in tufts. In crystalline form the 

 hemin-crystals of all varieties of blood examined are identical. They 

 are doubly refracting, appearing yellow and glistening under the 

 polarization-microscope, in contrast with their dark surroundings, 

 with marked absorption of the light parallel with the longitudinal axis 

 of the crystal. They are pleochromatic, that is, bluish-black and glisten- 



