62 IDENTIFICATION OF BLOOD. 



ing like polished steel in reflected light and mahogany-brown in 

 transmitted light. 



(1) Preparation from Dry Blood-stains. Several particles of the dry mass are 

 placed upon a glass slide, two or three drops of glacial acetic acid and a minute 

 crystal of sodium chlorid are added, and after the cover-slip has been placed in 

 position heat is carefully applied some distance above a spirit-lamp until a number 

 of small bubbles form. On cooling the crystals will be visible in the preparation 

 (Fig. 1 8). 



(2) Preparation from, stains upon porous bodies, from which the hemoglobin 

 cannot be scraped. The stained object fabric, wood is extracted with a dilute 

 solution of potassic hydrate and then with water. To both filtered solutions a 

 solution of tannic acid is added, and finally acetic acid until an acid reaction is pro- 

 duced. The resulting precipitate is washed upon a filter, then to a portion thereof 

 upon a glass slide a crystal of sodium chlorid is added, and the whole is dried. 

 Finally, the dried object is treated according to the method just described. 



(3) Preparation from Liquid Blood. The blood should always have been pre- 

 viously dried slowly and carefully. Then the process is continued as in the first 

 method. 



4 -A ^ ^ 



FIG. i"j. Hemin-crystals: i, from a human being; 2, from a 

 seal; 3, from a calf; 4, from a pig; 5, from a lamb; 6, 

 from a pike; j, from a rabbit. 



FIG. 18. Hemin-crystals Pre- 

 pared from Blood-stains. 



(4) Preparation from Dilute Solutions Containing Hemoglobin. To the fluid 

 is added ammonia, next tannic acid and then acetic acid until the reaction is 

 acid. A blackish precipitate of hematin tannate forms rapidly. This is washed 

 upon a filter with distilled water, then dried and heated in the same way as accord- 

 ing to the first method, except that instead of sodium chlorid a crystal of ammo- 

 nium chlorid is added. 



Not rarely at least small hemin-crystals can be obtained from putrid and lake- 

 colored blood, but under such circumstances the test often fails. Dried with iron- 

 rust, as upon weapons, blood usually no longer yields the reaction. Under such cir- 

 cumstances the matter is, according to Heinrich Rose, scraped away and boiled 

 with dilute potassium-hydrate solution. If blood be present the dissolved hematin 

 forms a fluid that in thin layers presents a bile-green color, but in thick layers a 

 red color. 



Hemin-crystals have been demonstrated in all classes of vertebrates, as well 

 as in the blood of the earth-worm. From some kinds of blood, as, for instance, 

 that of cattle and of swine, only irregular masses, scarcely recognizable as having 

 crystalline form, at times develop. Hemochromogen , hematoporphyrin, blood 

 rubbed with sand or animal charcoal, addition of certain salts of iron, lead, 

 mercury, and silver and lime prevent the development of the reaction. The 

 crystals of hemin are insoluble in water, alcohol, ether, and chloroform. They 

 are dissolved by concentrated sulphuric acid, with expulsion of hydrochloric acid 

 and the development of a violet-red color. They are dissolved by dilute alkalies. 

 If a solution of hemin-crystals in ammonia is evaporated, then heated to 130 C., 

 next treated with boiling water, which removes the ammonium chlorid formed, 



