HEMOGLOBIN 481 



Blood Pigments"" 



Red corpuscles behave much as do other non-nucleated fragments 

 of cells, undergoing disintegration rapidly and constantly when under 

 normal conditions, as well as when subjected to various harmful in- 

 jfluences (see "Hemoh^sis"), or when outside of the vessels in extrava- 

 sations of blood. The processes and products of their disintegration 

 arc, therefore, much the same whether occurring under normal or 

 pathological conditions. The hemoglobin molecule is large and com- 

 plex, and from it are derived many substances of the nature of pig- 

 ments; indeed, hemoglobin itself may appear free as a pigment. 



Hemoglobin is a compound protein, consisting of a protein group 

 {globin) and a coloring-matter {hematin or hemochromogen) .''^ The 

 protein globin is of a basic nature, and seems allied to the histons; 

 the hematin is, therefore, presumably acid. Hemoglobin ordinarily 

 does not crystallize readily, especially the hemoglobin of man, and it 

 is doubtful if it ever does so in the living tissues, although possibly 

 this may occur in the center of large hematomas. In bodies that have 

 undergone postmortem decomposition, and occasionally in specimens 

 kept for microscopic purposes, irregular orange-yellow crystalline masses 

 of hemoglobin may be found. This occurs particularly if the blood 

 has been acted upon by hemolytic agents or has undergone putrefactive 

 changes, and then is hardened in alcohol. The crystals are either 

 oxyhemoglobin, or more often an isomeric or polymeric modification, 

 parahemoglohin (Nencki). Hemoglobin also enters cells unchanged, 

 imparting a diffuse yellowish color, and apparently it is non-toxic. ^^ 

 If present in the blood in large enough amounts it is excreted un- 

 changed in the urine, but at least one-sixtieth of the total number of 

 red corpuscles must be in solution at one time to produce hemoglo- 

 binuria; in man at least 17 c.c. of laked corpuscles must be injected 

 to accomplish this." 



Addis^'* has developed the following conception of the metabolism 

 of hemoglobin. Free hemoglobin, liberated especially by the phago- 

 cytes of the spleen, is taken up by the other phagocytes, notably the 

 Kupffer cells of the liver, which pass it on to the liver cells. The 

 pigment moiety, hematin is separated from the globin, and converted 

 through removal of its iron into bilirubin. The bilirubin excreted into 

 the intestine is there reduced to urobilinogen, which is in part reab- 

 sorbed and polymerized into urobilin, which in turn is possibly poly- 

 merized into a larger complex. In the liver this urobilin complex has 

 restored to its pyrrol nuclei the original side chains, and then is used 



^"Literature by Schmidt, Ergebnisse der Pathol., 1894 (!■>), 101; and 1896 

 (nil), 542; Schulz, Ergebnisse der Physiol., 1902 (Ii), 505. 



'^ Halliburton and Rosenheim recommend that the name "hemochromogen" 

 be dropped in favor of "reduced hematin'.' (Biochem. Jour., 1919 (13), 195). 



72 Barratt and Yorke, Brit. Med. Jour., Jan. 31, 1914. 



" Sellards andMinot, Jour. Med. Res., 1916 (34), 469. 



'*Arch. int. Med., 1915 (15), 412. 



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