HYPERVITAMINOSIS A 619 



days or longer. However, the clotting time of these rats could be restored 

 to normal by the administration of an excess of ^■itamin K.^'^' While a 

 reduction in the incidence of the hemorrhages also followed vitamin K sup- 

 plementation, this treatment afforded no relief from the bone fractures. ^^^' 

 Quick and Stefanini^'-"^ are of the opinion that the excess vitamin A inter- 

 feres ^^dth the microbiologic synthesis of vitamin K by the intestinal flora. 

 In the case of the chick, which deri\'es its vitamin K exclusively from its 

 food, the coagulation time is not increased when 50,000 I.U. of vitamin A 

 are given. 



1205 A. J. Quifk and M. Stofanini, /. Biol. Chem., 175, 945-952 (1948). 



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