XIII. HKgUIUEMENTS 



511 



izod by chick assay, which were prepared from ciiliures of a bacterial 

 organism isohited from hen feces.-" Also in July 1948 it was reported that 

 vitamin B12 was effective at low levels in promoting growth in chicks on a 

 corn-soybean meal basal diet.-' These experiments showed that a crystalline 

 substance, vitamin Bn, had biological properties corresponding both to 

 those of the anti-perinicious anemia factor of concentrated liver extracts 

 and to the animal protein factor which was needed by chicks. Shortly there- 

 after it was tlemonst rated that vitamin B12 was active in promoting growth 

 in thyroid-fed rats-'- and that vitamin B12 could replace factor X for rats.^' 

 The requirement of chicks was found to be in the neighborhood of 10 to 

 20 7 of the crystalline substance per kilogram of diet. This corresponded 

 closely to the amount calculated from experiments with liver extract, since 

 from 1 to 2 7 of vitamin B12 when injected into a patient with pernicious 

 anemia produced a hemopoietic response corresponding to about 1 U.S. P. 

 unit, and about 0.5 to 1.0 ml. of concentrated liver extract, 15 units per 

 milliliter was found to provide adecjuate supplementation for chicks when 

 added to 1 kg. of corn-soybean meal diet.-* It was possible to compare the 

 effectiveness of oral and injected doses; about 0.37 7 when fed by pipet 

 weekly could be calculated to give a response corresi)()nding to 0.2 7 in- 

 jected intramuscularly. The requirement for vitamin B12 by the oral and 

 injected routes in normal chicks affords an interesting contrast with the 

 re(iuirements for pernicious anemia patients, if an arbitrary figure of 50 

 kilograms is taken from the l)ody weight of such patients: 



Approximate daily requirement of vitamin B12 per 

 kilogram of body weight 



Injected 



Oral" 



Pernicious anemia patients 

 ChicLs 



Witliout .sii|)pleiiii'nt!il iiitrin.sic factor. 



0.02-0.04 7 



0.27 



40-150 times the 

 minimum paren- 

 teral dose'' ^^ 

 0.4 7^' 



These calculations reveal that the pernicious anemia patient has a itiiich 

 smaller reciuirement per kilogram of body weight than normal chicks for 



"-' K. L. K. Stokstad, A. C. Pase, Jr., J. V. Pierce, A. L. Franklin, T. H. Jukes, R. 



W. Heinle, M. Epstein, and A. D. Welch, /. Lab. Clin. Med. 33, S60 (1948). 

 " W. 11. Ott, K. L. Rickes, and T. R. Wood, J. Biol. Chein. 174. 1047 (1948). 

 " G. A. Emerson, Pror. Soc. Exptl. Biol. Med. 70, 392 (1949). 



" A. M. Hartman, L. P. Dryden, and C. A. Gary, J. Am. Dietel. Assoc. 25, 929 (1949). 

 " E. L. R. Stokstad, T. H. Jukes, J. V. Pierce, A. G. Page, Jr., and A. b. Fratd<lin, 



J. Biol. Chem. 180, 647 (1949). 

 2"' G. G. Ungley, Brit. Med. J. 2, 905 (1950). 

 -^ L. M. Meyer, A. Sawitskj', B. S. Gohen, j\I. Krim, and R. Eadern, Am. J. Med. 



Sci. 220, 604 (1950). 



