XIII. REQUIREMENTS 523 



aiiinial origin, the nutritional needs must, presunial)!}', he met hy intestinal 

 l)acterial synthesis of the vitamin. The presence of relatively large amounts 

 of Bi2, or substances with B12 activity, has been demonstrated in the feces, 

 even in patients with pernicious anemia,'"-* but the (luantity present in the 

 contents of the small intestine is small.**" How much of the B12 produced 

 within the alimentary tract may be in an absorbable form or present at 

 sites favoral)le for absorption is unknown. 



Persons whose diets contain milk, eggs, and meat probably ingest a more 

 than adequate supplj' of B12. Thus, cow's milk was found to contain 6.G 7 

 per liter,*^' and the values for beef, pork, ham, mutton, and veal ranged 

 between 3 and 10 7 per 100 g.^^ 



Since B12 in a daily parenteral dose of 1 7 induces complete remission in 

 pernicious anemia patients,^'- ^^ the inference appears justified that the 

 normal daily requirement may be met by the absorption of 1 7 from the 

 alimentary tract. It appears probable, however, that only a fraction of the 

 B12 naturally present in food is absorbed even under normal digestive 

 conditions. 



79 R. H. Girdwood, Trans. Roy. Soc. Trop. Med. Hyg. 42, 65 (1948). 



8" R. H. Girdwood, Edinburgh Med. J. 58, 309 (1951). 



8> G. M. Briggs and R. J. Lillie, Federation Proc. 5, 124 (1946). 



^^ V. J. Lewis, U. D. Register, H. T. Tliompson, and C. A. Elvehjem, Proc. Exptl. 



Biol. Med. 12, 479 (1949). 

 «3 B. E. Hall and D. C. Campbell, Proc. Staff Meetings Mayo Clinic 23, 584 (1948). 

 8^ F. H. Bethell, M. C. Meyers, and R. B. Xeligh, J. Lab. Clin. Med. 33, 1477 (1948). 



