CHEMICAL EXAMINATION OF THE BLOOD. 337 



Like oxyhsemoglobin, methsemoglobin is capable of combining 

 with certain gases to form molecular compounds. Of these, a 

 carbon dioxide methcemoglobin, a methcemoglobin sulphide, and a cyan- 

 methcemoglobin have been described. Acetylene also is said to enter 

 into combination with the coloring-matter of the blood. These 

 compounds, however, are but little known. The metha3rnoglobin 

 sulphide results when hydrogen sulphide and air are simultaneously 

 passed through lake-colored blood. It gives rise to a greenish-red 

 color, and it is thought that . the greenish discoloration of decom- 

 posing bodies is referable to its presence. On spectroscopic exami- 

 nation its neutral solutions give two bands of absorption between 

 C and D, of which one is brighter and located near C, while the 

 other and darker band occupies the middle portion between C and 

 D. The two are united by a diffuse shadow. On adding a strong 

 solution of sodium hydrate the darker band disappears, and if now 

 the solution is heated and treated with a reducing agent, the spectrum 

 of haemochromogen results. 



The substance itself has not been isolated. 



Haematoporphyrin. This substance, as has been indicated, results 

 from hsematin when this is treated with concentrated sulphuric 

 acid that has been saturated with hydrobromic acid. During this 

 process the iron of the hsematin is split off, and a new pigment, 

 hsematoporphyrin, is formed. In the circulating blood of the verte- 

 brate animals it is not found under normal conditions, but is appar- 

 ently formed in certain diseases, and during the long-continued 

 administration of sulphonal and related bodies, as also in lead 

 poisoning and following intestinal hemorrhages, when it may also be 

 found in the urine. Among invertebrate animals it is said to occur 

 in the integument of the star-fish, in certain snails, in the earth- 

 worm, in various sponges, etc. 



Haematoporphyrin is thought to be isomeric with bilirubin, and is 

 thus represented by the formula C 32 H 36 N 4 O G . On reduction it yields 

 a pigment which is possibly identical with hydrobilirubin, or very 

 closely related to it. It may be obtained in crystalline form as 

 a hydrochlorate, while the pigment itself is amorphous. Its solu- 

 tions in acid alcohol present a beautiful purple color, which is 

 changed to a violet blue on adding an excess of the acid. It is 

 most conveniently obtained by starting with hsemin and decomposing 

 this with glacial acetic acid that has been saturated with hydro- 

 bromic acid. Its solutions in acid alcohol give two bands of absorp- 

 tion. One of these is located between C and D, while the second 

 band, which is much darker and more strongly defined, occupies 

 a position midway between D and E, and extends as a shadow 

 toward D. In dilute alkaline solutions, on the other hand, we find 

 four bands : one between C and D ; a second one, which is broader 

 than the first, between D and E and about D ; a third band, 

 between D and E, near E ; and finally a further band between b and 

 F, which is the widest and much darker than the rest. On treating 



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