540 XI. HEMOGLOBIN CATABOLISM, I 



of excreting bilirubin into the bile, admitted the possibility of bile 

 pigment formation in circulating blood by humoral factors. We have 

 seen above that some bile pigment is formed even in normal 

 erythrocytes. 



It may ultimately turn out that the biochemical conditions in the 

 cell together with its ability to take up hemoglobin are the decisive 

 factors, and that the histological origin is only of secondary impor- 

 tance. Wigglesworth {3081) noted bile pigment formation in the 

 epithelial intestinal cells of Rliodnius, as well as in its pericardial cells 

 which may be considered as precursors of reticuloendothelial cells. 



7.2. Bile Pigment Formation in Body Fluids 

 and Tissue Cultures 



In the earlier experiments on hemoglobin disintegration by tissue extracts 

 in vitro {92,397,1252) the products of the disintegration were not investi- 

 gated. The claims of Leschke {1721) that bilirubin formation in the cerebro- 

 spinal fluid continues in vitro was not confirmed by Duesberg {039). Other 

 early claims of bile pigment formation by extracellular enzymes have been 

 discussed by Rich {221f0), who showed that they were not convincing and 

 found no evidence of bile pigment formation by dead tissue or tissue extracts. 



Doljanski and Koch {609), however, claimed that chicken embryo extracts 

 converted hemoglobin to bilirubin, and in the light of subsequent work, and 

 of the ease with which oxyhemoglobin can be broken down by coupled oxida- 

 tion, it is possible that some of the earlier claims were correct. 



Reticuloendothelial cells cause the formation of bile pigments in 

 hemorrhagic transudates and hematomata; this occurs in mesothelial- 

 lined cavities, only rarely in epithelial-lined cavities {2989, p. 2473). 

 The bile pigment present in the sputum is probably of this origin. 

 Occasionally large amounts of bile pigments are thus formed patho- 

 logically {238,239,2238) and, in the placenta of the dog, also physio- 

 logically {1691). Practically nothing is known about the mode of 

 formation of biliverdin in birds' egg shells. 



Tissue culture experiments have given partly contradictory results 

 and should perhaps be repeated with more modern methods of iso- 

 lation and with greater attention to the formation of biliverdin. 

 Rich, Sumegi, and co-workers, and Niven {2056,2238,269^,2695) 

 found formation of bilirubin and hematoidin crystals in explanted 

 tissue of mesenchymic origin, e.g., spleen tissue of chicken embryo 

 and frog, when hemolyzed blood was added. Although Doljanski 

 and Koch {609) observed bilirubin formation in the embryonic 



