66 A MANUAL OF PHYSIOLOGY 



are due to the absorption of light of a definite range of wave-lengths 

 by metals in a state of vapour in the sun's atmosphere, and of course 

 no dark lines are seen in the spectrum of a gas-flame. Put some 

 defibrinated blood into a test-tube. Fasten it vertically in a clamp 

 in front of the flame and examine it with the spectroscope, holding 

 the latter in one hand with the slit close to the test-tube, and focus- 

 sing the eyepiece with the other. Or arrange the spectroscope, test- 

 tube and gas-flame on a stand as in Fig. 15. Nothing can be seen till 

 the blood is diluted. Pour a little of the blood into another test- 

 tube, and go on diluting till, on focussing, two bands of oxyh&moglobin 

 are seen in the position indicated in Fig. 7. Draw the spectrum ; 

 then dilute still more, and observe which of the bands first dis- 

 appears. Now put 5 c.c. of the blood into another test-tube, and 



FIG. 15. SPECTROSCOPIC EXAMINATION OF BLOOD-PIGMENT. 



dilute it with four times its volume of water. Take 5 c.c. of this 

 dilution, and again add four times as much water, and so on till the 

 solution is only faintly coloured. Note with what degree of dilution 

 the bands disappear. Then examine each of the solutions with the 

 spectroscope and draw its spectrum. 



(b) Make a solution of blood which shows the oxyhaemoglobin 

 bands sharply. Add some ammonium sulphide solution to reduce 

 the oxyhaemoglobin. Heat gently to about body temperature. A 

 single, ill-defined band now appears, occupying a position midway 

 between the oxyhaemoglobin bands, and the latter disappear. This 

 is the band of reduced hemoglobin (Fig. 7). 



(c) Carbonic Oxide Hemoglobin. Pass coal-gas through blood for 

 a considerable time. Examine some of the blood (after dilution) 

 with the spectroscope. Two bands, almost in the position of the 

 oxyhcemoglobin bands, are seen ; but no change is caused by the 



