PLATE I. 





1. Solar spectrum with Fraunhofer lines. 2. Absorption spectrum of a concentrated solution of oxyhemo- 

 globin ; all the light is absorbed except in the red and orange. 3. Absorption spectrum of a less concentrated 

 solution of oxyheraoglobin. 4. Absorption spectrum of a dilute solution of oxyhemoglobin, showing the two 

 characteristic bands. 5. Absorption spectrum of a very dilute solution of oxyhemoglobin, showing only the 

 a-band. 6. Absorption spectrum of a dilute solution of reduced hemoglobin, showing the characteristic single 

 band (to be compared with spectrum 4). 7. Absorption spectrum of a dilute solution of carbon-monoxid- 

 hemoglobin (to be compared with spectrum 4). 8. Absorption spectrum of methemoglobin. 9. Absorption 

 spectrum of acid hematin (alcoholic solution). 10. Absorption spectrum of alkaline hematin (alcoholic solu- 

 tion) (modified from MacMunn, The Spectroscope in Medicine) . 



