140 THE BLOOD 



tion of the corpuscles is the pigment known as hemoglobin, and this is the 

 only chemical factor that will be considered in these experiments. 



a. Hemoglobin Crystals. Take a sample of dog's blood, or if a centri- 

 fuge is available separate and wash the sample of blood-corpuscles, and 

 mix with about three volumes of saturated ether water, or if blood is used dilute 

 with two or three volumes of water and add about 10 per cent of pure ether 

 and shake thoroughly. Crystals of oxyhemoglobin will be formed, and this 

 can be mounted and examined with a microscope. 



b. Spectrum of Hemoglobin and its Compounds. 



1. Oxyhemoglobin. Dilute a sample of defibrinated blood with about 

 ten volumes of distilled water. From this stock solution make five solutions 

 all differing by 33^ per cent. Examine these with a direct-vision spectroscope. 

 Make a drawing showing the absorption spectrum of each sample as com- 

 pared with the solar spectrum. Compare with the spectrum shown in the 

 frontispiece. 



2. Hemoglobin. The oxygen can be driven out from the hemoglobin 

 by adding to the above samples a few drops of ammonium sulphide and 

 gently warming. Re-examine with the direct-vision spectroscope and map 

 as before. 



3. Carbon-Monoxide Hemoglobin. Pass a stream of ordinary illumi- 

 nating gas through the dilutions of hemoglobin. The carbon monoxide 

 of the gas will form a compound with the hemoglobin, which now turns a 

 bright scarlet color. When examined with the spectroscope, the absorp- 

 tion bands are found to be very similar to those of oxyhemoglobin. How- 

 ever, map the spectrum to the scale as usual. Add the reducing agent, 

 warm, and shake vigorously and re-examine. It is very difficult to break up 

 the combination of hemoglobin with carbon monoxide, hence the poisonous 

 action of this gas. 



