STORAGE OF CAROTENOIDS AND OF VITAMINS A 475 



suffering from folliculosis, even after high dosages of vitamin A.'"^ Chieffi 

 and Kirk^*^ found that hyperkeratosis of the skin folhcles, and local con- 

 junctival thickening occurred with greater frequency in subjects having a 

 low plasma vitamin A (1 to 15 iig. % or 3 to 50 I.U.) than in those having 

 a higher plasma vitamin A level (25 to 60 ng. % or 83 to 200 I.U.)- How- 

 ever, no correlation could be demonstrated between the plasma vitamin A 

 level and the number of epithelial cells excreted daily in the urine, and no 

 relationship was observed between plasma vitamin A and the proportion 

 of keratinized cells in the urinary sediment. Blood vitamin A, and the 

 factors which influence it, are more completely treated in The Lipids, Vol. 

 II, pages 366 to 369 and 486 to 509. 



6. The Storage of Carotenoids and of Vitamins A 



Carotenoids are widely distributed in the plant kingdom, both in the 

 higher forms and in the grass-green varieties of algae (Chlorophiita) ,^^^ and 

 in the parasitic "red-snow" ascomycetous fungus {Chlamydomonas ni- 

 valis). ^^^ They are present to a lesser extent in animals. Larger amounts 

 are found in the lower forms of animal life than occur in the tissues and fat 

 depots of the higher forms. On the other hand, vitamin A is exclusively 

 an animal product, which has an exceedingly wdde distribution in prac- 

 tically all species of animals. For a discussion of the distribution of carote- 

 noids in plant and animal sources, the reader is referred to The Lipids, 

 Vol. I, pages 507 to 666, while the distribution of vitamin A in animals is 

 included on pages 675 to 713 of that treatise. Reference is especially made 

 to the monographs of Williams, ^^^ of Goodwin, ^^^'^^^ and of Fox^^^ for the 

 most complete information on carotenoids in plants, invertebrates and 

 vertebrates. Other reviews on this subject include the treatises of Rosen- 

 berg,i With,^^ Lederer,^^'' and Fox.^^^ Goodwin^^- reviewed the biogenesis 

 of carotenoids. 



^ M. Chieffi and E. Kirk, /. Nutrition, 37, 67-79 (1949.) 



3«« G. M. Smith, The Fresh-Water Algae of the United States, 2nd ed., McGraw-Hill, 

 New York, 1950, pp. 19-23, 39-41, 110-111. 



^' R. J. Williams, The Significance of the Vitamin Content of Tissues, Vitamins and 

 Hormones, 1, 229-247 (1943). 



3«s T. W. Good«-in, Biol. Revs. Cambridge Phil. Soc, 25, 391-413 (1950). 



^' D. L. I'ox, Animal Biochromes and Structural Colours, Cambridge Univ. Press, 

 1953. 



^^ E. Lederer, Les Carotenoides des Animaux, Hermann, Paris, 1935. 



"1 D. L. Fox, Ann. Rev. Biochem., 16, 443-470 (1947). 



392 T. W. (toodwin, /. Sci. Food Agr., 4, 209-220 (1953). 



