DISTRIBUTION OF BILE PIGMENTS IN NATURE 569 



The verdohemochrome found in certain cytochrome c preparations 

 is an artefact, probably derived from altered, autoxidizable cyto- 

 chrome c (Lemberg and Wyndham, 1716). 



There is more evidence for catalase undergoing a breakdown to 

 bile pigments, which has been discussed in Chapter IX, Section 2.3. 

 and Chapter X, Section 8.2. 



The breakdown of myoglobin has been discussed in this chapter 

 (cf. Sections 7.4. and 9.3.3.). The formation of porphyrins from 

 myohemoglobin in pathological conditions, and possibly from cyto- 

 chrome c, will be discussed in Chapter XII. 



12. DISTRIBUTION OF BILE PIGMENTS IN NATURE 



Thus far we have discussed the formation of bile pigments from 

 hemoglobin in vertebrates, mainly in mammals. Far less is known 

 about the formation of bile pigments in other living forms, but the 

 few isolated observations when pieced together indicate that bile 

 pigments are widespread in nature. Often we have no knowledge of 

 their origin, as for example with regard to the bile pigments forming 

 the prosthetic groups of the algae chromoproteins phycoerythrin and 

 phycocyanin or of the chromoprotein of butterfly wings (c/. Chapter 

 IV, Section 7.2.). Metcalf (1917) has recently claimed that chloro- 

 phyll is broken down to a green bile pigment in the squash bug 

 (Anasa tristis), but the claim is based merely on a positive Gmelin 

 reaction. In other instances, however, it is evident that the bile pig- 

 ments originate from hematin compounds by the same kind of 

 mechanism which transforms hemoglobin into bile pigment. 



In Section 2.3. we referred to the observation of Virtanen and Lane {2891) 

 on choleglobin formation in root nodules, and to the observations of Wiggles- 

 worth {3081) on the breakdown of liemoglobin in .several blood-sucking 

 insects, e.g., the louse, but particularly in the reduviid bug Rhodnius {cf. 

 also Mouchet, 1903). In Rhodnius small amounts of hemoglobin pass into 

 the hemolymph, where hematin is found in the form of a hem/chrome. This 

 has evidently no biological function in the insect, but nevertheless it is 

 metabolized in a manner closely akin to the catabolism of hemoglobin in 

 vertebrates. Choleglobin and biliverdin are observed, biliverdin is excreted 

 in the intestine and is partly transformed into urobilin, while injected hemo- 

 globin is excreted as biliverdin in the Malpighian tubes, a primitive kidney. 

 Biliverdin has also been observed in the peritoneal cells of the leech {2604) 

 and in the digestive tract of invertebrates io94), although in the leech as 

 well as in Rhodnius the greater part of the hematin is excreted as such. 

 Similarly Raphael {2206) found biliverdin accompanying large amounts of 



