198 THE BLOOD. 



which have undergone this last change exhibit, when placed 

 before the slit of the spectroscope, in place of the haemoglobin 

 bands, a less distinct and paler band on the opposite side of 

 the D line, ?'. e., in the orange. This change is characteristic 

 of the presence of haematin. It is attended with an obvious 

 darkening of the color of the liquid. 



When an alkaline solution of haematin is subjected to the 

 action of reducing agents, such as sulphuret of ammonium or 

 protosulphate of iron, it exhibits, when examined spectroscopi- 

 cally, two much more distinct bands (Fig. 195, 4), one of which 

 is exactly opposite the bright space which separates the two 

 haemoglobin bands ; the other, which is less intense, is close to 

 Frauenhofer's line, E, i. e., nearer to the blue end of the spec- 

 trum than the broader of the two haemoglobin bands. If the 

 solution is fresh and dilute, and the quantity of the reducing 

 agent small, these bands can be made to vanish by agitation 

 with air, giving way to the so-called oxyhaematin band above 

 described. All these facts may be as readily demonstrated in 

 solutions of blood corpuscles ; i. < J ., of cruor, as in solutions of 

 haemoglobin. Blood rendered distinctly alkaline cither by soda, 

 potash, ammonia, or their carbonates, shows the absorption 

 band of oxyhaematin. After addition of sulphuret of ammo- 

 nium, this is replaced by the more distinct spectrum of reduced 

 haematin. 



22. Hsematoin. When acetic acid is added to blood, the 

 iron of the haemoglobin is separated and takes the form of a 

 protosalt, and a new coloring matter remains in solution, the 

 spectrum of which was first described by Professor Stokes, and 

 has been subsequently known as acid haematin. More recently, 

 Preyer has shown that it is not identical with ha?matin, but 

 with the body to which Hoppe-Seyler gave the name of iron-free 

 haematin. It is produced whenever V-oncentrated sulphuric 

 acid acts on haematin. According to Hoppe-Seyler, it is pre- 

 pared by rubbing up finely powdered haematin in concentrated 

 sulphuric acid. A liquid is obtained which is green in thin 

 layers, reddish-brown in thicker layers, and gives a brown pre- 

 cipitate when diluted with water. This precipitate is easily 

 dissolved in ammonia. On evaporating the ammoniacal solu- 

 tion, a bluish-black residue with metallic lustre is left, which is 

 free from iron. It ma} 7 be obtained in like manner by acting 

 on metha3moglobin by sulphuric acid. The solution of haema- 

 toin in ammonia exhibits four absorption bands. It is ad- 

 mirably shown by the method recommended by Professor 

 Stokes, i. e., by extracting with ether blood which has been 

 mixed with acetic acid. The ethereal liquid thus obtained ex- 

 hibits a four-banded spectrum. Of these bands, three only are 

 easy to recognize one in the orange, nearer to the red than 

 the reduced haematin band ; a rather broad band in the green; 



