INTRODUCTION 629 



isolate them in pure form. Ergosterol provides an exception to this rule, 

 as does the so-called provitamin Dn,, recently isolated by Petering and 

 Waddell^- from the ribbed mussel {Arcuaiula (Modiola) demissa). Accord- 

 ing to the data of Bills,- the proportion of the total sterols which are pro- 

 vitamins D are usually under 6% in the vertebrates; in the case of inverte- 

 brates, proportions of provitamins D as high as 8% occur in the Cnidaria, 

 21% in the Annelida, 12% in the Arthropoda, and 37% in the case of one 

 type of Mollusca {Arcuatula demissa). On the other hand, the maximum 

 proportion of provitamin D was only 0.45% of the total sterol in the Echino- 

 dcrmata. Plant sources included among the Phanerogams also had a very 

 low proportion of provitamins D (maximum of 2.8% of total sterol), but in 

 the case of the Cryptogams, practically 100% of the sterols were provitamins 

 D (see Table 1). The quantitative results of Windaus^^ of Gillam and 

 Heilbron,^* and of van der Vliet,^^ as summarized by Bills, in Sebrell and 

 Harris, 2 are given in Tables 2 and 3. 



c. Occurrence of Specific Provitamins D. (a) Ergosterol. Tanret^^ 

 was the first to describe a sterol in the parasitic fungus ergot (Claviceps 

 purpurea) in 1879; because of its source, it was called ergotinine and later 

 ergosterine.^'' This investigator recognized that it differed in composition 

 from cholesterol and from the phytosterols.^^ Gerard^^-^*"" reported the dis- 

 tribution of ergosterol in a wdde variety of plants; he found that there was a 

 taxonomic relation in the occurrence of this sterol, since it was character- 

 istic of the cryptogams just as the phytosterols are characteristic of the 

 phanerogams. According to Heidushka and Lindner/"^ the ergosterol con- 

 tent of ten fungi, including yeasts, was found to vary between 0.29 and 

 1.17% of the dry matter. Bills and co-workers^"- observed an ergosterol 

 content varying from a trace (in Saccharomyces logos, which ferments meli- 

 bose) to as much as 2% of the dry material (in Saccharomyces carlshergensis, 



« H. G. Petering and J. Waddell, /. Biol. Chem., 191, 765-773 (1951). 

 ^3 A. Windaus, Nachr. Ges. Wiss. Gottingen, Math.-physik. Klasse, Fachgruppe III, 

 n.s. 1, 185-192 (1936). 



" A. E. Gillam and I. M. Heilbron, Biochem. J., 30, 1253-1256 (1936). 



95 J. van der Vliet, Chem. Weebkad, 39, 271-276 (1942); Chem. Zentr., 1942, II, 1353. 



96 C. Tanret, Ann. chim. phys. [5], 17, 493-512 (1879). 



97 C. Tanret, Compt. rend., 108, 98-100 (1889). 



98 C. Tanret, Ann. chim. phys. [6], 20, 289-297 (1890). 



99 E. G6rard, Compt. rend., 114, 1544-1546 (1892); 121, 723-726 (1895); 126, 909- 

 911 (1898). 



10" E. Gerard, /. pharm. chim., [6], 1, 601-608 (1895). 



101 A. Heidushka and H. Lindner, Z. physiol. Chem., 181, 15-23 (1929). 



102 C. E. Bills, O. N. Massengale, and P. S. Prickett, J. Biol. Chem., 87, 259-264 

 (1930). 



