ANIMAL CHLOROPHYLL 373 



association with chlorophyll. It was first isolated from carrots 

 (sometimes spelled ' carrotin '), from which it received its name. 



Willstatter und Meig (1907) have shown that carotin is 

 a crystalhne unsaturated hydrocarbon (C4„ Hgg) melting at 

 174°. It is of wide occurrence not only in the vegetable, but 

 also in the animal kingdom, being found in the blood sera 

 of most birds and mammals (Schunck, 1903 ; Palmer, 1915, 

 1916 ; and Hymans van den Bergh und Miller, 1920), and in 

 mammalian milk ; ^ the yellow pigment of butter fat likewise 

 is composed largely of carotin (Steenboch, Sell, and Buell, 

 1921). It is also found in manmialian ovaries ; however, the 

 ' lutein ' of the corporea lutea themselves is isomeric with 

 xanthophyll, the oxide of carotin. The colored substance 

 of egg-yolk is made up largely of xanthophyll, though it too 

 contains some carotin (Palmer and Kempster, 1919 a, h, and c) ; 

 carotin also is sometimes present in human urine, appearing 

 there after carotin has been ingested (Hess and Meyers, 1919), 

 and it has been isolated from gall-stones (Plimmer, 1915, 

 p. 532). But of much greater interest is the fact that carothi 

 is present abundantly in manmialian nerve-cells (Dolley and 

 Guthrie, 1919 a and h), and in the fovea centralis of the human 

 eye. Also the yellow pigment cells (xantholeucophores) in the 

 epidermis of Fundulus contain carotin, but what concerns 

 us more immediately is its occurrence in the chromatophores 

 of crustaceans. 



Blanchard (1890) made it evident that the epidermal pig- 

 ment of the copepod Diaptomus lacillifer contains 

 a large percentage of carotin. Keeble and Gamble (1902, 

 1904, and 1905) have corroborated this result, finding that the 

 chromatophores of many other crustaceans also possess the 

 pigment. They noted, too, that mobile fat globules are usually 

 to be found in the branching pigment cells. It has been shown 

 by Kohl (1902) that carotin was capable of photosynthesizing 

 fats. With this fact before them, Keeble and Gamble made 



1 Pahner and Eckle.s (1914) have shown that the amount of carotin 

 and xanthophyll in milk (human and cow) is in exact proportion to the 

 amount of green food consumed. 



