LIPOCIIROMES 479 



are probably soluble in fats, and in this way t lie lipofusfins are formed.*' 

 In the renal epithelium is found a pigment resembling the lipofuscins, 

 increasing with age and not related to the urinary pigments." 



Typical plant lipochromes, as also the pigments 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 colored green. Lipochrome of 

 frog-fat stains blue with this 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 pig- 

 ments of the other tissues mentioned above do not give either of these 

 reactions. Possibly these last are not true lipochromes, therefore, 

 but rather pigments 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. Melanins 

 and pigments derived 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. Apparently carotin and xan- 

 thophyll (a crystalline pigment from green plants) ^"^ are the chief 

 pigments of milk fats, egg yolk, and probably of body fats.^^ In the 

 body lipins these pigments accumulate throughout life because of 

 their great solubility in lipins, which explains the high color of the fats 

 of old persons. Carotin seems to be almost or quite devoid of toxicity, ^^ 

 and in persons eating carrots in large C|uantities there may be enough 

 pigment present in the blood {carotinemia) to produce skin pigmenta- 

 tion resembling jaundice.^" 



The work of Palmer indicates that carotin and xanthophyll are 

 much more widely distributed than was formerly appreciated. Ani- 

 mals with colored fats owe the color to these plant pigments, which 

 are also present in the blood of these same animals, but not in the blood 

 of animals with colorless fats (swine, rabbits, dogs, sheep, goats), and 

 the so-called lipofuscin of the ganglion cells has been shown to be 



^^ Ciaccio (Biochem. Zeit., 1915 (69), 313) agrees with Hueck, and finds it 

 possible to distinguish between pigments from phosphatids, which stain poorly 

 with Sudan III, and those from free fatty acids which stain deeply with this dye. 



" Schrever, Frankf. Zeit. Pathol., 1914 (15), 333. 



" Virchow's Arch., 1902 (170), 363. 



" Compt. Rend. Soc. Biol., 1903 (55), 812. 



" Zeit. physiol. Chem., 1913 (83), 198. 



" Concerning plant pigments see review by West and Horowitz,Biochem. Bullet., 

 1915 (4), 151 and 161. 



^^ See articles by Palmer and Eckles, Jour. Biol. Chem., 1914, Vol. 17 et seg. 



58 Wells and Hedenburg, Jour. Biol. Chem., 1916 (27), 213. 



" Hess and Myers, Jour. Amer. Med. Assoc, 1919 (73), 1743; see also ibid., 

 1920 (74), 32. 



