Pigmentation. 



211 



dissolved coloring matter may pass into the urine, producing 

 hcEmoglohiniiria and methcemoglobimiria, in which conditions the 

 urine assumes a bloody, dark-red or brownish black appearance. 

 Precisely as in normal life, the dead blood cells and their remnants 

 are taken up by leucocytes and carried to the lymph nodes, spleen, 

 bone marrow and elsewhere; in cases of exaggerated destruction 

 of the erythrocytes the same methods of transportation are car- 

 ried on in greater measure, and the renmants of hsemoglobin are 

 deposited in the various organs in proportion as this blood refuse 

 fails of complete destruction. Some of these derivatives retain 

 their iron (hceniosidcriii), as shown by microchemical reactions 

 (blackened by ammonium sulphide ; bluish green color on addition 

 of yellow^ ferrocyanide of potassium) ; others contain no iron 

 (hcemoftiscin and bilirubi)i) and may be seen as yellowish or brown 

 granules and clumps or as a diffuse, rust-colored or yellowish im- 

 pregnation of the tissues. 



Hsemcglobin crystals from the blood of a 

 dog killed by chloroform inhalation ; 

 X 2.50. (After TTioma.) 



Fig. 32. 



IIa?matoidin crystals from a 

 large centrally softened 

 blood extravasation in the 

 peritoneal cavitv : X 2.jU. 

 (After Thoma.) 



Haemorrhagic foci give rise to very profuse hematogenous pig- 

 mentation, both the minute extravasations arising by diapedesis 

 and the larger haemorrhages ; depending upon the amount of color- 

 ing matter deposited and the age of the lesion they cause a 

 rusty, ochre-like to black or slate-colored discoloration of the 

 tissues. The haemoglobin at first diffuses from the escaped blood 

 corpuscles and soaks through (is imbibed by) the tissues in the 

 neighborhood of the haemorrhagic focus ; the washed out cor- 



