L/I'OCHROME 475 



by osiiiic aeitl ; they are dissolved by the usual fat solvents. It is 

 questionable if all pigments that stain for fat should be considered as 

 true lipochromos, however, for their other reactions are variable; 

 and Rorst would distin<;-uisli these path()lo<i-i('al pigments from the 

 true lipochromes by calling them lipofuscins, including under this 

 term the brown "waste pigments," which Hueck believes to be 

 formed from disintegrated lipoids or fatty acids. Many pigmentary 

 substances are probably soluble in fats, and in this way the lipofus- 

 cins are formed.'''"' Ty})ical plant lipochromes, inchuling the pig- 

 ments of Staphylococcus pyogenes aureus and citreus, are colored blue 

 by concentrated sulphuric acid with formation of small blue crystals 

 of lipocyanin. With iodin-potassium-iodide solution they are col- 

 ored green. Lipochrome of frog-fat stains blue with the iodin-potas- 

 sium-iodide solution (Neumann) ; •''•* lipochrome of the corpus luteum 

 (called lutein) occasionally gives a faint blue with sulphuric acid or 

 Lugol's solution (Sehrt) ; but the fat-holding pigments of the other 

 tissues mentioned above do not give either of these reactions. Pos- 

 sibly these last are not true lipochromes, therefore, but rather pig- 

 ments chemically or physically combined with fat. Cotte *° believes 

 that the true lipochromes of plants and animals have a cholesterol 

 base, but the presence of glycerol in plant and bacterial lipochromes 

 can be demonstrated by the acrolein test — possibly, therefore, both 

 cholesterol and neutral fats are present. iMelanins and pigments de- 

 rived from hemoglobin do not stain with Sudan III and are not soluble 

 in ether, etc., and hence can be readily distinguished from the fatty 

 pigments. It has been shown by Escher **'"* that the pigment of the 

 corpus luteum is identical with the carotin of carrots. Apparent!}' 

 carotin and xanthophyll (a crystalline pigment from green plants)**"' 

 are the chief pigments of milk fats, e^^ yolk, and probably of body 

 fats.^^ In the bod}^ lipins these pigments accumulate throughout 

 life because of their great solubility in liiiins, which explains the 

 high color of the fats of old persons. Carotin seems to be almost or 

 quite devoid of toxicity.*^'' In the renal epithelium is found a pig- 

 ment resembling the lipofuscins, increasing with age and not related 

 to the urinary pigments.*^*^ The pigment of nerve cells resembles 

 that produced during autolysis in ganglia. •*^'= 



The pigment that causes the peculiar green color characteristic 



asa Ciaccio (Biochem. Zeit.. 1015 (fiO), .31.3) agrees with Hueck, and finds it 

 possible to distinguisli between pigments from phospliatids, whieli stain poorly 

 with Sudan III, and tliose from free fattv acids which stain deeply with tiiis dve. 



39Virchow's Arch.. 1002 (170), 363. 



•loCompt. Rend. Soc. Biol.. 1003 (5.1). S12. 



4oaZeit. phvsiol. Chem.. 1013 (S3), lOS. 



40b Concerning plant pigments see review bv West and Horowitz, Biocliem. 

 Bullet., 1915 (4), 1.51 and 101. 



41 See articles by Palmer and Eckles, Jour. Biol. Chem. 1014, Vol. 17 et seq. 



4ia Wells and Hedenburg, .lour. Biol. Chem., 1016 (27), 213. 



41b Schreycr, Frankf. Zeit. Pathol., 1014 (1.5). 333. 



41C Marinesco, C. R. Soc. Biol., 1013 (72), 838. 



