IX. REQUIREMENTS 



165 



iiiji i)ptimal j^row tli is aijproxiiuatcly 100 I.U. per kil()<>;iani of Ixxly wcij^ht 

 ulu'ii \itaiiiiu A i« led. When carotene is to serve as the source of tlie \ita- 

 niin, a considerably larj^er amount is required. Irving and Richards" have 

 reported data which they interpret as meaning an increase in vitamin A 

 requirement with age. The results obtained by Little et a/.,'" where liver 

 storage was measured following the feeding of graded doses of vitamin A, 

 would seem to support this hypothesis. However, it is possible that the 

 results obtained mereh^ represented a greater requirement as the body size 



Level fed 



TABLE XVIII 

 Estimates of the Vitamin A Requirement of the Rat 



Criterion used 



References 



6,2 



7 



8 



7 



7 



9 



6,2 



10 

 11 



8 

 8 

 8 



12 

 13 



of the animals increased. Of considerable interest are the results obtained 

 by Sherman'^ where growth, longevity, and reproductive period were 



6 H. Goss and H. K. Guilbert, J. Nutrition 18, 169 (1939). 

 ^ E. C. Callison and V. H. Knowles, .4m. J. Physiol. 143, 444 (1945). 

 « J. M. Lewis, O. Bodansky, K. (i. Falk, and G. McGuire, J. Xutrition 23, 351 (1942). 

 9 H. E. Paul and M. F. Paul, ./. Nutrition 31, 67 (1946). 



'0 R. W. Little, A. W. Thomas, and H. C. Sherman, J. Biol. Chem. 148, 441 (1943). 

 '• P. B. Horton, W. A. Murrill, and A. C. Curtis, J. Clin. Invest. 20, 387 (1941). 

 '2 H. C. Sherman and H. L. Campbell, Proc. Natl. Acad. Sci. U. S. 31, 164 (1945). 

 •' H. C. Sherman and H. Y. Trupp, J. Nutrition 37, 467 (1949). 

 " J. T. Irving and N. B. Richards, Nature 144, 908 (1939). 



'^ II. C. Sherman, H. L. Campl)ell, M. Udiljak, and II. Varmolinsky, Proc. Natl. 

 Acad. Sci. U. S. 31, 107 (1945). 



