44 



A MANUAL OF PHYSIOLOGY 



haemoglobin is in the oxidized state in the state of oxyhaemo- 

 globin, as it is called. If the oxygen is removed by means of 

 reducing agents, such as ammonium sulphide, or by exposure 

 to the vacuum of an air-pump, the colour darkens, the blood- 

 pigment being now in the form of reduced haemoglobin. In 

 ordinary venous blood a large proportion of the pigment is in 

 this condition, but there is always oxyhaemoglobin present as 

 well. In asphyxia (p. 231), however, nearly the whole of the 

 oxyhaemoglobin may disappear. 



B C 



Oxyhaemoglobin 



Reduced haemoglobin 



Carbonic oxide 

 haemoglobin 



Methaemoglobin (in 

 acid solution) 



Acid-haematin (in 

 ethereal solution) 



Alkaline-haematin 



Hasmochromogen 



Haematpporphyrin 

 (in acid solution) 



Haematoporph yrin 

 (in alkaline solu- 

 tion) 



** i .umiiiimimii| [f ] j 



B C Q F 



FIG. 7. TABLE OF SPECTRA OF HEMOGLOBIN AND ITS DERIVATIVES. 



Crystallization of Haemoglobin. In the circulating blood the 

 haemoglobin is related in such a way to the stroma of the corpuscles 

 that, although the latter are suspended in a liquid readily capable of 

 dissolving the pigment, it yet remains under ordinary circumstances 

 strictly within them. In a few invertebrates, however, it is normally 

 in solution in the circulating liquid. As a rare occurrence haemo- 

 globin may form crystals inside the corpuscles (p. 63). When it is in 

 any way brought into solution outside the body, it shows in many 

 animals, but not in the same degree in all, a tendency to crystalliza- 

 tion ; and the ease with which crystallization can be induced is in 

 inverse proportion to the solubility of the haemoglobin. Thus, it is 



