Experiments on Vitamin A 



201 



which conferred the most intense passive hypersensitiveness in 

 guinea pigs, and lowest in the serum (anti-"alkaline antigen") 

 which conferred the lowest hypersensitiveness. With edestin the 

 precipitin titrations were reversed. The rabbit serum prepared 

 with "acid antigen," although more effective in sensitizing guinea 

 pigs, gave lower precipitin titrations than either of the sera pre- 

 pared against "unadjusted" or "alkaline antigen." The indica- 

 tions from these experiments are that modifications in the hydro- 

 gen-ion concentration may simultaneously affect anaphylactogenic 

 and precipitinogenic potencies of different proteins differently. 

 Some of the questions raised by these observations are being 

 studied further. 



99 (2059) 



Experiments on vitamin A. 



By H. C. SHERMAN and M. M. KRAMER. 



[From the Department of Chemistry, Columbia University, 

 New York City.] 



These experiments relate chiefly to questions concerning the 

 storage of vitamin A in the body and the bearing of this upon 

 methods of examining foods to determine their relative richness 

 in vitamin A. 



Even at weaning time young animals may already have a 

 considerable store of vitamin A in the body and thus be able to 

 continue to grow for some time upon a diet carefully freed from 

 vitamin A but adequate in all other respects. Young rats sepa- 

 rated from their mothers at a uniform "weaning" age of four 

 weeks show very different growth curves and survival periods 

 on the same experimental diet free from vitamin A, according 

 to the vitamin A content of the mother's diet. The differing 

 stores of vitamin A in the bodies of experimental animals, even 

 at early ages, has undoubtedly been a very large factor, not fully 

 appreciated, in previous experiments dealing with this vitamin 



