54 PRACTICAL PHYSIOLOGY. [VI. 



(d.) The sjiectrura shows four absorption-bands ; a faint band midway be- 

 tween C and D, another similar one between D and E, but close to D ; a third 

 baud near E ; and a fourth one, darkest of all, occupying the greater part of 

 the space between b and F, but nearer the former. 



In all cases make drawings of what you see, and compare them with the 

 table of characteristic spectra suspended in the laboratory. 



18. Picro-Carmine. — Its spectrum closely resembles that of 

 HbOg, but the two bands are much nearer the violet end, one 

 being midway between D and E, and the other to the violet side of 

 E. The bands are unchanged on addition of Am^S or Stokes's 

 fluid. The solution does not give proteid reactions. 



ADDITIONAL EXEECISES. 



19. Prolonged Action of Methsemoglobin-forming Reagents. — Allow 

 KMn04, KgFeCyg, iodine, amyl or potassium nitrite or glycerine to act on HbO.j 

 for some days at 40^ C. Methaemoglobin is first formed, then haematin. The 

 latter is partially precipitated. Precipitate may be washed with water and 

 dissolved in dilute acid or alkali. In the case of EgFeCye the solution becomes 

 cherry-red, and contains cyan-haematin. Its spectrum shows one broad band, 

 like that of Hb, between D and E, unchanged on shaking with air. In the case 

 of amyl nitrite the final product in solution has a spectrum like that of HbOg, 

 unchanged on treatment with Am.S (? HbNO). 



HbOo solution or dilute blood left on the water-bath at 40° C. for some days 

 shows first a partial formation of methaemoglobin and later becomes Hb. It 

 does not become converted into haematin {J. A. Menzies). 



20. Effect of Sodium Fluoride. — To BhO^ solution or diluted blood, add a 

 few drops of i per cent. NaFl solution, and keep at 40° C. until the colour 

 changes from scarlet to a rich crimson. Examine the spectrum. In addition 

 to traces of the HbOo bands, there will be seen two bands, one very distinct to 

 the red side of D, slightly nearer the red than the band of alkali-haematin, the 

 other, not easily seen, to the violet side of E. On addition of Am^S, the spec- 

 trum changes first to that of HbO.2, then Hb. 



21. Effect of Acids. —(a.) To 15 cc. dilute blood which gives a well-marked 

 spectrum of HbO.2, add 5 drops of i per cent. HCl (or other acid). The colour 

 changes to brown, and the spectrum to that of acid haematin. Add ammonia, 

 the spectrum becomes that of alkaline methaemoglobin, and, on addition of 

 Am.jS, the solution changes to HbO, then Hb. But, if Am^S be added witli- 

 out" previous addition of ammonia, the spectrum becomes that of haemo- 

 chromogen first becoming Hb on standing, and then RhO^ appears on shaking 

 the solution with air, 



{b.) Place 15 cc. of solution of pure HbOa with well-marked spectrum in 

 each of five test-tubes. To these add i, 2, 5, 10, and 15 drops of i per cent. 

 HCl respectively. Place all on a water-bath at 40° C. for 24 hours, or longer 

 if necessar}'. In some of the tubes a precipitate of haematin will be found, and 

 in one of these the supernatant fluid will be colourless, and will give proteid 

 reactions. Decant the colourless fluid, and collect and wash with water the 



