VT. occruKKxrE 103 



incstic animals are largely ivd with Inddei', the diviiiji process has l)eeii 

 cxainiiied intensively with r(>j>;ard to tiie provitamin content.'-'-" In the 

 Inited States, alfalfa, I'resh and dry, plays a great roh" in snpplxing these 

 animals wilii \-itamins A. 



In all plants the provitamins A are accompanied hy carolenoids which 

 are biologically inactixc; this is of great importance foi' the chemical and 

 physical analysis. Human anil animal organisms show an accunnilation of 

 \itamin A in the liver and tlu^ kidneys as well as in the milk and in the 

 Mood (see Tal)le XMI). Both \itamin A and carotene aic found in the 

 human and animal oi-ganisni and its secretions along with biologically in- 

 actix'e carotenoids.-'- 



Fish liver oils, being particularly rich in \itamin A, are the only natural 

 source for commercial extraction. According to recent results, the livers of 

 polar bears are the richest source of vitamin A known so far. They are so 

 rich in vitamin A as to cause poisoning by hypervitaminosis; 0.5 to 0.7 g. of 

 polar bear liver per rat may kill.-^ The reasons why these animals and fish 

 store vitamin A in such large amounts are not yet known. 



It is unlikely that the organism of the fish is able to cany <.ut a true 

 biosynthesis of vitamin A. It is assumed that fish ingest carotenoids with 

 the food i)lankton and lower plants, algae, and crustaceans, and then convert 

 tlu>se into vitamin A. The himian being and the higher animals do not have 

 an ability to transform carotenoids of non-provitamin A type into vitamin 

 -V. It .seems to be proved that many carnivorous animals, e.g., cats, are not 

 capable of transforming provitamins A into vitamin A.--* Such animals 

 ha\-e no other soiu'ce for this \-itamin than the organs and the blood of their 

 prey. Milk is relatively rich in vitamin .\ and so are all fat-containing milk 

 l^roducts. In this case the vitamin .\ content is .subject to seasonal fluctua- 

 tions depending on whether fresh (sumnuM-) or dry (winter) foddei' has been 



'■- .\. 1{. Kciniiicicr and (i. S. Ftaps, /tul. Eiuj. ('In in. Aiuil. K>l . 38. l.')? (1046). 



'^ II. L. Mitchell and H. H. King. .7. Hiul. Chnn. 166, 477 (1<)4()). 



' II. L. .Mitchell, W. G. Schrenk, and H. 11. \\m^. Arch. Biochem. 16, 34:^ (11)48). 



'^ 1.. A. .Mnoi-e. !,hI. Emj. Chcm. .\n<iI. E<I . 12, 720 (1940). 



"■■ 11. C. 11. (iraves, Chimistrii A' I ikIusI nj 61. S (1042). 



'■ F. P. Zsch.'ile, H. W. Beadle, and II. T. Krayhill. F<H,d livsntrch 8, 20!) (1043). 



"* A. K. Kenimeier and G. S. Flaps, Food licxcdich 10, 457 (104o). 



'" A. K. Kemmeror. G. S. Fraps, and W. W. Meinke, Food Rcsrorrli 10, (Hi (1045). 



1'.. I), i:zell and .M. S. Wilco.x, Food Ucsrarch 13, 203 (1948). 



.\. 1{. Kenunerer and G. S. Fraps. /iid. Fn<i. Chnn. Anal. Kd . 15, 714 (10431. 

 " H. v..n lluler, H. v..n Ihiler. and 11. ilellslroni, Blorhmt. Z. 202, 370 (1930): A. K. 



Gillam and M. S. Kl Hidi. Hiochnn. ./ . 29, 24<i5 (1935). 

 " K. Hodahl and T. Moore. Biochou . J .37 , l(i() (1043); K. Kodahl, iMh International 



Physiological Congress, Copenhagen, 1050: Z. (iiujtir. ('In m. 63, 7S (1051 ). 

 ^' n. Ahmad, Biochem. .7. 25, 1195 (1931). 



