XXI.] THE COLOUR OF BLOOD. RESPIRATION. 225 



8. Examine the spectrum of blood-crystals either 

 with the microspectroscope or by placing a thick 

 layer of crystals on a glass slide before the larger 

 spectroscope. The spectrum of oxyhaemoglobin 

 is seen. 



9. Pass carbonic oxide through an oxyhaemoglobin 

 solution for fifteen to thirty minutes. 



a. Note the peculiar bluish tinge acquired Ex- 

 amine the spectrum; two bands are seen 

 like those of oxyhaemoglobin, but both placed 

 more towards the blue end; the middle of 

 (a) is about w. L. 572, of () about w. L. 535. 

 In the absence of a wave-length spectroscope, 

 oxyhaemoglobin and CO -haemoglobin may be 

 compared as follows. Place some of the oxy- 

 haemoglobin solution before the spectroscope, 

 bring the micrometer wire to the middle of 

 one of the bands, and fix the telescope in 

 position. Replace the oxyhaemoglobin solu- 

 tion by the carbonic oxide haemoglobin solu- 

 tion and examine; the middle of the band 

 will now be to the blue side of the wire. 



b. Treat the carbonic oxide haemoglobin with 

 either of the reducing agents used above. 

 Reduction will not take place. 



10. Take a few c.c. of a solution of crystals of haemo- 

 globin. 



a. Boil; the proteid constituent will be co- 

 agulated. 

 L. 15 



