IX. OCCURRENCE IN FOOD 477 



Foods and feed that do not contain Foods and feed tliat do contain 



the still unidentified factor the unidentified factor 



White flour Milk 



Enriched white flour Skim milk (liquid or dried) 



Whole-wheat flour Cheese (cottage, Swiss, Cheddar) 



Yeast (baker's or brewer's) Liver extracts 



Wheat bran Beef muscle 



Corn meal (yellow) Pork muscle 



Soybean oil meal Egg yolk 



Linseed oil meal Lettuce 



Egg white (heat-coagulated) Alfalfa and alfalfa hays 



Carrots Timothy hays 



Tomatoes Kentucky bluegrass 



The presence of the factor in the green leafy materials listed above is not 

 in accordance with results reported by other investigators who used bio- 

 logical assays with rats, chicks, or bacteria. 



Zucker and Zucker^ made an extensive study of the distribution of 

 "zoopherin," now presumed to be identical with vitamin B12, by measuring 

 the growth of young rats weaned from mothers on an all-vegetable diet. 

 Hog liver and calf liver were found to be very good sources, and good 

 amounts of zoopherin were present in other meat products including beef 

 round, calf spleen, and calf thymus. Various marine animals including 

 starfish, oysters, the eggs of Artemia salina, winkles, and sand worms also 

 contain substantial amounts of zoopherin. 



FoUowmg the isolation of vitamin B12 and the development of the L. 

 leichmannii' • ^ and Euglena gracilis,^ microbiological assay procedures, ex- 

 ploration of the distribution of the vitamin in foods was greatly accelerated. 

 Some information is present m Table XVII. It is not known to what extent 

 the microbiological assay values were complicated by the presence of 

 pseudo-vitamin Bi2.^° However, it is evident that most green leafy materials 

 contain no vitamin B12 detectable by the sensitive Euglena gracilis assay. 



From the broad standpoint vitamin B]2 may be regarded as a substance 

 which is produced by microorganisms and not by the higher plants. Its 

 existence in animal tissues occurs as a result of the ingestion, directly or 

 indirectly, of products of microbial fermentation. The presence of vitamin 



8 T. F. Zucker and L. M. Zucker, Vitamins and Hormones 8, 1 (1950), 



' C. E. Hoffmann, E. L. R. Stokstad, A. L. Franklin, and T. H. Jukes, J. Biol. 

 Chem. 176, 1465 (1948). 



8 H. R. Skeggs, H. M. Nepple, K. A. Valentik, J. W. Huff, and L. D. Wright, /. 

 Biol. Chem. 184, 211 (1950). 



» S. Hutner, W. Provasoli, E. L. R. Stokstad, C. E. Hoffmann, M. Belt, A. L. Frank- 

 lin, and T. H. Jukes, Proc. Soc. Exptl. Biol. Med. 70, 118 (1949). 



'» J. J. Pfiffner, D. G. Calkins, R. C. Peterson, O. D. Bird, V. McGlohon, and R. W. 

 Stipek, Ahstr. Papers, 120th Meeting, Am. Chem. Soc, p. 22C (1951). 



