30 REDUCTION OF HEMOGLOBIN. 



[The two absorption-bands lie between the lines D and E, the band 

 nearer D being more sharply defined and narrower than the second 

 band, which is wider and less clearly marked-off, and lies nearer E.] 



It occurs in the blood-corpuscles, circulating in arteries and capillaries, 

 as was shown by the spectroscopic examination of the ear of a rabbit, of 

 the prepuce and the web of the fingers (Vierordt). 



Reduction of Oxyhaemoglobin. It gives up its O very readily, how- 

 ever, even when means which set free absorbed gases are used. It is 

 reduced by the removal of the gases by the air-pump, by the conduction 

 through its solution of other gases (CO & NO), and by heating to the 

 boiling point. In the circulating blood its is very rapidly given up 

 to the tissues, so that in suffocated animals only reduced haemoglobin 

 is found in the arteries. Some constituents of the serum and sugar 

 use up 0. By adding to a solution of oxyhsemoglobin reducing sub- 

 stances e.g., ammonium sulphide, ammoniated tartarate of zinc oxide 

 solution, iron filings, or Stokes's fluid [tartaric acid, iron proto-sulphate, 

 and excess of ammonia] the two absorption bands of the spectrum dis- 

 appear, and reduced hcemogloUn (gas-free) (Fig. 11, 4), with one absorp- 

 tion band is formed (Stokes, 1864). [The single band which is obtained 

 from reduced haemoglobin lies between D and E, and its most deeply 

 shaded portion is opposite the interval between the two bands of oxy- 

 hsemoglobin. Its edges are less sharply defined. The colour of the 

 blood changes from a bright red to a brownish tint. Hoppe-Seyler 

 applies the term HcemogloUn to the reduced substance to distinguish it 

 from oxy haemoglobin.] 



The two bands are reproduced by shaking the reduced haemoglobin 

 with air, whereby O 2 Hb is again formed. Solutions of oxyhsemoglobin 

 are readily distinguished by their scarlet colour from the purplish tint 

 of reduced haemoglobin. 



If a string be tied round the base of two fingers so as to interrupt the circulation, 

 the spectroscopic examination shows that the oxyhsemoglobin rapidly passes into 

 reduced Hb (Vierordt). Cold delays this reduction (Filehne). 



The spectroscopic examination of small blood-stains is often of the utmost 

 forensic importance. A minimal drop is sufficient. Dissolve in a few drops of 

 distilled water, and place in a thin glass tube in front of the slit of the spectroscope. 



(2.) Methsemoglobin (Hoppe-Seyler) contains more than oxy- 

 haemoglobin (Fig. 11,5). Chemically it is fairly stable, contains 0, and 

 crystallises (Hiifner and J. Ott). It is obtained by acting upon a 

 solution of reduced or oxyhsemoglobin with oxidising reagents ; best, 

 however, by adding crystals of potassic ferridcyanide. It shows four 

 absorption bands like an acid solution of haematin, that between C and 

 D being the only one sharply defined. 



If a trace of ammonia be added to such a solution, it gives an alkaline solution 

 of methsemoglobin, which shows two bands like oxyhaemoglobin, of which the first 



