74G VIII. PROVITAMINS D AND VITAMINS D 



lichens.*^'** It is almost certain that the mushroom substance investigated 

 many years ago by Braconnot,^^ Vauquehn,^^ and Gobley^^ Mas ergosterol. 

 Zellner^^ reported a number of additional varieties of mushrooms Avhich 

 contain ergosterol. The most practical source of this sterol is dried yeast, '"" 

 in which ergosterol makes up 90 to 100% of the total sterols."^ Ergosterol 

 may also be found in some of the higher plant forms. Thus, it has been 

 reported to comprise 5% of the non-saponifiable fraction of cottonseed oil, 

 while its proportion of the total sterols in Scopolia root amounts to 1.4%.''^ 

 Although the main sources of ergosterol are undoubtedly the cryptogams, 

 there are well-authenticated instances in which it is found in the animal. 

 It has been proved that ergosterol comprises 19 to 25% of the sterols in the 

 red snail {Arion empiricorium) ,^^^'^^^ while 22% of the sterol content of the 

 earthworm {Lumhricus terrestris) has been found to consist of this sterol. 

 Windaus and Stange^"^ also noted that ergosterol is to be found in the hen 

 egg, although it is believed that its presence in this source is a reflection of 

 the ergosterol which has been ingested. A similar explanation has been ad- 

 vanced to explain the presence of vitamin Do in eggs, inasmuch as this is not 

 the natural form of vitamin D in this species. Bethke and co-workers ^°'''"'* 

 noted that vitamin D may be found in the tissues and egg-yolks of hens 

 fed irradiated ergosterol or cod liver oil, the type of vitamin D found de- 

 pending upon that present in the feed. The same variations were also 

 reported in milk, coincident with variations in the type of vitamin D in the 

 diet.^°^ Small amounts of vitamin D2 have been isolated from fish liver 

 oils by Brockmann and Busse,'"^ although the chief vitamin here is vitamin 

 D3. 



(2) 7-Dehydrocholesterol 



7-Dehydrocholesterol is the most prevalent provitamin D in the higher 

 animals and man. Boer and co-workers^^ were the first to demonstrate the 

 presence of this sterol as a contaminant in cholesterol of unknown origin. 

 That it is a naturally occurring product is indicated by the results of 



95 C. Tanret, Ann. chim. phys. [8], 15, 313-330 (1908). 



96 H. Braconnot, Ann. chun. phys. [1], 79, 265-304 (1811). 

 " M. Vauquelin, Ann. chim. phys. [1], 85, 5-25 (1813). 



98 M. Gobley, J. pharm. chim. [3], 29, 81-91 (1856). 



99 J. Zellner, Chemie der hoheren Pilze, Engelmann, Leij^zig, 1907. 

 «» C. Tanret, Compt. rend.. 14?, 75-77 (1908). 



101 A. Windaus, Nachr. Ges. Wiss. Gottingen, Math, physik. Klasse, HI, 185-192 (1936). 

 10* F. Bock and F. Wetter, Z. physiol. Chem., 256, 33-41 (1938). 

 103 A. Windaus and O. Stange, Z. physiol. Chem., 2U, 218-220 (1936). 

 10* R. M. Bethke, P. R. Record, C. H. Kirk, and D. C. Kennard, Poultry Sci., 15, 326- 

 335 (1936). 



105 R. M. Bethke, P. R, Record, O. H. M. Wilder, and C. H. Kirk, Poultry Sci., 15, 

 336-344 (1936). 



106 R. M. Bethke, W. E. Krauss, P. R. Record, and O. H. M. Wilder, /. Nutrition, 11, 

 21-30 (1936). 



107 H. Brockmann and A. Busse, Z. physiol. Chem., 256, 252-270 (1938). 



