A. G. Hogan 155 
contains 0.90 per cent. On the other hand, such evidence as is 
available points strongly to the complete absence of lysine from 
zein. Osborne and Leavenworth (1913) found no trace. Further- 
more, according to a theory advanced by Van Slyke and Birchard 
(1914), proteins containing lysine possess free amino groups that 
react with nitrous acid; but zein gives no evidence of such a 
reaction. Gliadin, on the contrary, according to their data 
yields 1.10 per cent of the total nitrogen as free amino nitrogen. 
Although this evidence may be questioned, yet such weight 
as it has is all against the presence of lysine in the zein complex. 
If the facts deduced from zein feeding contradict our findings 
while feeding kafirin, we have no explanation for the discrepancy. 
SUMMARY. 
Lysine is the first limiting factor in kafirin and cystine is the 
second. 
Lysine is indispensable for the maintenance of young animals. 
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Hogan, A. G., J. Biol. Chem., 1917, xxix, 485. 
Johns, C. O., and Brewster, J. F., J. Biol. Chem., 1916-17, xxvii, 59. 
Mathews, A. P., Physiological Chemistry, New York, 1915, 110. 
Osborne, T. B., and Leavenworth, C.S., J. Biol. Chem., 1918, xiv, 481. 
Osborne, T. B., and Mendel, L. B., J. Biol. Chem., 1914, xvii, 325. 
Osborne and Mendel, J. Biol. Chem., 1915, xx, 351. 
Osborne and Mendel, J. Biol. Chem., 1916, xxv, 1. 
Osborne, T. B., Van Slyke, D. D., Leavenworth, C. 8., and Vinograd, 
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Totani, G., Biochem. J., 1916, x, 382. 
Van Slyke, D. D., and Birchard, F. J., J. Biol. Chem., 1913-14, xvi, 539. 
Wheeler, R., J. Exp. Zool., 1913, xv, 209. 
Willcock, E. G., and Hopkins, F. G., J. Phystol., 1906-07, xxxv, 88. 
