THE BLOOD n 



oxygen, and the explanation which has been offered is that while 

 the oxygen is united to the pigment portion of the molecule, the 

 carbon dioxide is united to the protein portion. 



When examined spectroscopically, oxy- and reduced haemo- 

 globin produce quite distinctive spectra, by which they may be 

 readily recognised. To state the matter broadly, oxyhemoglobin 

 gives two well-marked dark absorption bands or shadows in the 

 green portion of the spectrum, one band being wide, the other 



Oxyhemoglobin 



Reduced haemo- 

 globin 



Carbonic oxide 

 haemoglobin 



Methaemoglobin (in 

 acid solution) 



Acid haematin (in 

 ethereal solution) 



Alkaline haematin 



Haemochromogen 



Haematoporphyrin 

 (in acid solution) 



Haematoporphyrin 

 (in alkaline solu- 

 tion) 



Fig. 2. — Table of Spectra of Hemoglobin and its Derivatives 

 (Stewart). 



narrow, while reduced haemoglobin gives one wide single band in 

 nearly the same position (Fig. 2). The change from oxy- 

 haemoglobin to reduced haemoglobin may readily be brought 

 about in spectroscopic examination by the addition of an alkaline 

 solution of ferrous tartrate (Stokes's fluid) to the blood. 



Crystals of haemoglobin, when seen in bulk, are of a dark red or 

 bluish-red colour ; they are extremely soluble in water, the solu- 

 tion being dichroic — viz., green by reflected and bluish-red by 

 transmitted light. The blood of the horse, cat, dog, and guinea- 



