CHAXGES IN THE INTESTINAL AVALL 441 



tion. The liver of a monitor lizard {Varamis comodensis) , which had eaten 

 almost nothing durmg a six-month voyage from Commodo Island to Den- 

 mark, contained large amounts of vitamin A. A cetacean, the grampus or 

 "Risso's dolphin" {Grampus griseus) stores insignificant amounts of vi- 

 tamin A. The mole {Talpa europaea) and the bat (Vespertilio, spp.) store 

 a large amount. They subsist mainly on insects and worms; apparently 

 insects are a rich source of vitamin A. Dogs and cats store a considerable 

 amount, but not as much as do the wild fox (Canis vulpes) and fitchet or 

 fichew {Mustela putorius), which is a European polecat. 



There is some evidence that cattle, which normally have high levels of 

 blood and liver carotene, and which likewise may secrete large amounts of 

 this provitamin into the milk, also have the capacity to convert carotene to 

 vitamin A in the intestinal wall.^^" It would thus appear that the pro- 

 vitamins A occur in the blood and tissues of some species, not because the 

 intestinal wall lacks the capacity for splitting carotene, but because a con- 

 siderable proportion escapes the gut wall before it has been transformed into 

 vitamin A. 



It is generally agreed that some sites for changing carotene to vitamin A, 

 other than the walls of the small intestine, must exist for species whose 

 tissues and blood contain considerable proportions of carotenoids. The 

 liver and reticuloendothelial (RE) systems have been cited as the most 

 probable sites for this reaction. 



Moore^^ believes that he had demonstrated the presence of an enzyme, 

 called "carotenase," in the liver of dogs; this enzyme catalyzed the caro- 

 tene — >■ vitamin A reaction. Positive results on vitamin A sjiithesis from 

 carotene were also demonstrated by Pariente and RaUi,^^" who used the dog- 

 liver carotenase, by v. Euler and Klussmann^^^ in cow's hver, and by Wil- 

 son et al}^- in the liver of rabbits. On the other hand, the results were 

 completely negative in the case of the Atlantic spiny dogfish (Sqiialus 

 acanthius) and black goby {Gobius niger), as cited by v. Euler and v. 

 Euler, ^^^ and in the cat, according to Rea and Drummond,^^"* or rabbit, 

 reported by Druimnond and MacWalter. ^^^ Olcott and McCann^^^ did 

 report positive evidence of the change in rat liver sUces. However, these 



150 A. C. Pariente and E. F. Ralli, Proc. Soc. Exptl. Biol. Med., 29, 1209-1210 (1931- 

 1932). 



'" H. V. Euler and E. Klussmann, Svensk Kern. Tidskr., U, 223-224 (1932). 



•" H. E. C. Wilson, B. Ahmad, and B. M. Mazumdar, Indian J. Med. Research, 25, 

 85-88(1937). 



1" B. V. Euler and H. v. Euler, Svensk Kern. Tidskr., 43, 174-178 (1931). 



'"J. L. Rea and J. C. Drummond, Z. Vitaminforsch., 41, 177-183 (1932). 



'66 J. C. Drummond and R. J. MacWalter, Biochem. J., 27, 1342-1347 (1933). 



i5« H. S. Olcott and D. C. McCann, /. Biol. Chem., 94, 185-193 (1931). 



