244 DISTURBANCES OF CIRCULATION 



globin, the decomposition of the hemoglobin in the tissues is 

 probably accomplished in a similar way by the proteases of the 

 leucocytes, tissue-cells and blood plasma ; the globin is thus 

 digested away and the soluble products carried off, while the 

 insoluble hematin remains. 1 The hematin gradually undergoes 

 further changes, forming an iron-free pigment (hematoidin) and 

 an iron-containing pigment (hemosiderin). 



Hematoidin is nearly or quite identical with the bile-pig- 

 ment, bitirubin, and is absorbed from the hemorrhagic extrava- 

 sation and eliminated as bilirubin in the bile. Possibly some 

 of the hematoidin undergoes transformation into urobilin, and 

 is then eliminated in the urine, Hemosiderin seems to be rela- 

 tively insoluble and, therefore, is more slowly removed, so that 

 it may be found at the site of a hemorrhage after the other 

 evidences of blood extravasation have been removed. It may 

 be easily demonstrated by staining with potassium ferrocyanide, 

 the Prussian blue that is formed being readily distinguished. 

 Unstained hemosiderin generally appears in the form of brown 

 or yellowish-brown granules, never as crystals. After a time 

 the hemosiderin is taken away, and probably is to a greater or 

 less extent deposited in the liver and spleen, either as hemo- 

 siderin or as some other iron compound. Eventually it is prob- 

 ably utilized to make new hemoglobin ; at any rate, the iron 

 liberated by the breaking up of hematin within the body does 

 not appear to be eliminated. 2 



The changes in the red corpuscles described above are not at 

 all peculiar to extravasated blood, but are quite the same as 

 the changes that are going on continuously and normally in the 

 blood. Red corpuscles are short-lived, being but non-nucleated 

 fragments of cells, and they are continually disintegrating with 

 the production of iron-free pigments that are excreted as the 

 coloring-matters of the bile and the urine, while the iron is 

 worked over again into new hemoglobin after a varying period 

 of storage in the tissues, particularly in the spleen and liver. 

 The destruction of red corpuscles under normal conditions seems 

 to take place chiefly in the spleen, bone-marrow, and hemolymph 

 glands, where injured or decrepit corpuscles are taken out of 

 the blood by the phagocytic endothelial cells, and decomposed 

 by intracellular enzymes. In hemorrhagic extravasations the 

 changes are essentially the same ; some corpuscles are destroyed 

 by phagocytes, but more by extracellular enzymes. The prod- 

 ucts of decomposition also seem to be no different from those 



1 More fully discussed in the consideration of " Pigmentation," Chap. xvi. 

 'See Morishima, Arch. f. exp. Path., 1898 (41), 291. 



