242 MANUAL OF PHYSIOLOGY. 



bonic oxide. The CO occupying the place of the oxygen, thus 

 destroys the function of the blood corpuscles. CO-haemoglobin 

 may be distinguished from O-haemoglobin by not being reduced 

 by reagents greedy of oxygen, and by the bright red color which 

 appears when 10 per cent, solution of caustic soda is added, and 

 the mixture heated. O-haemoglobin gives a muddy brown color 

 under the same treatment. 



DECOMPOSITION OF HAEMOGLOBIN. 



Haemoglobin may easily be broken up into two constituents 

 namely, (a) a colorless substance which is nearly related to the 

 class of proteids called globulin, and (6) a blackish red amor- 

 phous material called Hceanatin, which contains all the iron of 

 the haemoglobin. 



This change is brought about by whatever causes the coagula- 

 tion of albumin, such as the addition of acids, strong alkalies, 

 and heat to 70 C. 



H^MATIN, ETC. 



Haeraatin is a secondary product, being the result of the oxida- 

 tion of a substance called haemochromogen, which is the first out- 

 come of the decomposition of the haemoglobin. Hsemochromogen 

 can only be obtained in an atmosphere of hydrogen or nitrogen, as 

 it immediately takes up oxygen to form haematin. The formula 

 CesHfoNgFgOjo has been given for haematin. It dissolves in weak 

 alkaline and acid solutions, but not in water or in alcohol. 



Haematin is readily prepared by mixing acetic acid with a 

 strong solution of haemoglobin, which becomes a dark-brown 

 color. The dark haematin can be removed by ether. But if the 

 acid used be strong, the solution of haematin is found to be free 

 from iron. This iron-free haematin Preyer calls hcBtnatoin. If, now, 

 the acid haematin solution be saturated with ammonia, the iron 

 again becomes united with the haematoin, forming alkali-haematin. 



H^EMIN. 



Haematin unites with hydrochloric acid to form a crystalliz- 

 able body called hcemin or hydrochlorate of hsematin (Teich- 

 mann's crystals). 



