OCCURRENCE OF PROVITAMINS D 



747 



Windaus and Bock,''^ who were able to separate it from pigskin, where it 

 makes up 3 to (3% of the total sterols. Just how far down the scale of the 



TABLE 1 

 Provitamin D ('ontent of V'arious Animal and Plant Materials" 



" Adapted from H. R. Rosenljerg, The Chemistry and Physiology of the Vitamins, 

 Interscience, New York, 1945, p. 347. 



animal kingdom it is to be found is uncertain; however, its appearance may 

 coincide with that of ergosterol, since one species of whelk, Buccinum 

 undalum, contains this provitamin. ^"^-^"^ 



