330 BIOLOGICAL EFFECTS OF RADIATION 



The genetic series is probably best summarized in the following 

 diagram. This is based mainly on the papers by Windaus and his 

 colleagues, particularly Setz. There is some evidence that the scheme 

 is not complete. Between lumisterol and tachysterol a protachysterol 

 may occur. The reviewer has assumed that substance 248 precedes the 

 suprasterols, because the absorption spectrum of overirradiated sub- 

 stance 248 (Bills, Honeywell, and Cox, 12) is essentially that of the 

 suprasterols studied by the German workers. The name, calciferol, is 

 retained for that form of vitamin D which has been isolated. It is not 

 impossible that at least one other form of the vitamin occurs in crude 

 irradiation product. 



Ergosterol 



i 

 Lumisterol 



i 

 Tachysterol 



i 

 Vitamin D (calciferol) 



i 

 Toxisterol (substance 248) 



^ \ 

 Suprasterol I Suprasterol II 



1. ^rgfosieroZ.— C28H43OH; |7; m.p. varies with hydration; XX 2600, 

 2700, 2820, 2935 A; {a\^\l^ = -174°; [af^ = -135° in chloroform. 



Ergosterol, the parent substance of the series of irradiation products, 

 has been prepared in high purity by Bills and Honeywell (11) and 

 Callow (19). It forms colorless crystals which tenaciously retain water 

 of crystallization. Commercial specimens of otherwise good quality 

 contain about 5 per cent of a-dihydroergosterol (Callow, 20). 



2. Lumisterol— C^.'RisOB.; jl; m.p. 118°; XX 2650, 2800 A; [aUl = 

 -\-2S5A° ■,[aYo = +191.5° in acetone. 



Crude irradiation product, after removal of unchanged ergosterol by 

 treatment with methyl alcohol or digitonin, is a nearly colorless resin. 

 In the separation of vitamin D from this resin, a substance was recovered 

 which was called sterol X by the English workers and given the name 

 Lumisterin by the Germans. It was studied in considerable detail by 

 Windaus, Dithmar, and Fernholz (94), who obtained it by the fractional 

 crystallization of the acetate of the lumisterol-calciferol addition com- 

 pound. The absorption spectrum of lumisterol is similar to that of 

 ergosterol in range and intensity, but it shows only two maxima, instead 

 of four. Lumisterol appears to be the initial product of the irradiation 

 of ergosterol. It probably is devoid of antirachitic action, but it is 

 converted by irradiation into vitamin D. It forms with calciferol a 



