52 PRACTICAL PHYSIOLOGY. [VI. 



alkalUisematin, Stokes' s reduced hsematin or hsemochromogen, 



and observe its spectrum ; two absorption-bands between D and 

 E, as with Hb0 2 and HbCO, but they are nearer the 

 violet end. The first band to the violet side of the I) 

 line is well defined, while the second band, still nearer 

 the violet end (in fact, it nearly coincides with the 

 E line), is less defined. They disappear on shaking 

 vigorously with air, and reappear on standing, pro- 

 vided sufficient ammonium sulphide be added. 



A 



Hsemochromogen and Hsematin. Seal up in a glass tube 

 a solution of oxy -haemoglobin with caustic soda. Hoppe-Seyler 

 recommends the following method but it is unnecessary. Ar- 



KHO range a tube as in fig. 29. Place some hemoglobin solution 

 in A, and into a narrower cup-shaped glass tube (B), with a 

 long stem place some NaHO, and place B inside A, as shown 

 in the figure. Draw out the end ot tube A in a gas- flame, and 

 seal it in the flame. Mix the two solutions. At the end of 

 three weeks break off the narrow end of the tube, and shed 

 the contents upon a white plate. The contents consist of red 



B hsemochromogen, but the latter, as soon as it is exposed to 

 the air, becomes brown, and is converted into hsematin. 



16. VI. Methsemoglobin (fig. 30). 

 (a.) To a medium solution of oxy-hoemoglobin add 

 a few drops of a freshly-prepared strong solution of 

 ferricyanide of potassium (or a i per cent, solution of 

 A potassic permanganate), warm gently, observe the 

 change of colour, and examine it with a spectroscope. 

 If the two bands of oxy-haemoglobin are still present, 

 FIG. 29. Appara- allow it to stand for some time and examine 

 again. If they persist, carefully add more ferri- 

 cyanide until the two bands disappear. Note 

 one absorption-band in the red near C, nearly in the same posi- 

 tion, but nearer I) than the band of acid hsematin; the violet 

 end of the spectrum is much shaded. Three other bands are 



no 



FIG. 30. Spectrum of Methaemoglobin in Acid and Neutral Solutions. 



described, two in the green, and one in the blue, especially in 

 dilute solutions. On adding ammonia to render the solution 

 alkaline, the band in the red disappears, and is replaced by a 

 faint band near D. 



