The vitamin A1 and A2 contents of mammalian and other animal livers

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Abstract
Spectroscopic examination of extracts of livers showed that mammal and bird livers contain vit. A1 but no A2. In the 21 spp. examined the only exceptions found were Varanus salvator (considerable A1 and only traces of A2) and animals known to feed on fish, i.e., Phoca vitulina and Lutra vulgaris. A mammalian liver exceptional in that it contained more A2 than A1 was obtained by feeding a rat with a concentrate of freshwater fish liver. This indicates that although mammals cannot metabolize vit. A2 they can pass it into the liver if they receive it preformed into their digestive tract. The vit. A1 content of all the livers examined fell within the rather narrow limits of 0.7-32 mgm. per 100 gm. fresh liver (average for 18 spp.=8.3 mgm. per 100 gm.) with the exception only of Python reticulatus, V. salvator, and L. vulgaris with values of 86, 250 and 47 respectively.