RIBOFLAVINE 



mg. per loo g., and the dorsal subcutaneous tissue 2-4 to 3-05 n:ig. 

 per 100 g. The eye, on the other hand, which, from the association 

 between ariboflavinosis and eye lesions in mammals, might have been 

 expected to be a particularly good source of the vitamin, contained 

 only o-i to 07 mg. per 100 g. 



There appears to be a close connection between the occurrence in 

 tissues of melanin and riboflavine, the above high values being observed 

 only with crustaceans that were heavily pigmented. Species con- 

 taining no melanin generally contained no riboflavine ; riboflavine 

 was also found to be absent from the skin of albino animals. In the 

 lower vertebrates, on the other hand, the melanocyte was very rich 

 in riboflavine, reaching a value of 10 mg. per 100 g. in tissue from 

 batrachians. Among higher vertebrates, however, including man, the 

 riboflavine content of the melanocyte was very low, not exceeding 

 0-2 mg. per 100 g. of tissue. 



The following values were recorded for different kinds of meat : 

 beef, 0-04 to 0*35 ; pork,^'' 0-09 to 0-35 ; rabbit, o-o6 to 1-2 ; mutton, 

 0-27 ; and chicken ,^s 0-05 to 0-35 mg. per 100 g. Ox kidney con- 

 tained 0-8 to 2-0 ; ox liver, o-i to 3-0 ; pig liver,^' 4-4 ; and sheep's 

 liver, 17 mg. per 100 g. 



In general, the liver and kidney of the pig, ox, calf and lamb were 

 richer than other organs and tissues ^^ in riboflavine. The liver, 

 heart and gizzard of the chicken were likewise richer than the leg or 

 heart muscle. ^*^ 



Beef extracts contained the bulk of the riboflavine originally 

 present in the fresh meat, five commercial samples containing 1-5 to 

 2-6 mg. per 100 g., so that a breakfast-cup made with a teaspoonful 

 of extract would supply up to 0-25 mg. of riboflavine. Corned beef 

 was correspondingly poorer in this factor, containing 0*07 to o-i8 mg. 

 per 100 g., that is, about one-fifth of the quantity present in roast 

 beef.2i 



Dried yeast is, next to crustacean tissue, the richest known edible 

 source of riboflavine, values up to 12-4 mg. per 100 g. being recorded. 

 Brewers' yeast was richer than bakers' yeast, and Torula richer than 

 brewers' yeast, which generally contained about 5 mg. per 100 g.22 

 The riboflavine in live yeast was not available, however, for animal or 

 human nutrition and only partial absorption of riboflavine took place 

 from two dried yeasts containing living cells. ^^ Heating rendered the 

 riboflavine available. 



Many other fungi were relatively rich in riboflavine,^* containing 

 up to 0-69 mg. per 100 g. Eremothecium Ashhyii (see page 150) 

 contained considerably more than any other micro-organism tested, 

 values up to 264 mg. per 100 g. of the moist material being recorded ; ^s 

 it is probably the richest of all known sources. 



166 



