634 X. VITAMINS D 



proximately 22% of the sterols of the earthworm (Lumbricus terrestris) have 

 also been shown to consist of ergosterol. Ergosterol has likewise been iso- 

 lated from the bodies of the Roman land snail (Helix pomatia) .'^'^'' How- 

 ever, there is some question as to the universal occurrence of ergosterol in 

 the earthworm. Boer and co-workers^"*-^"^ reported that "spectroscopi- 

 cally pure" provitamins of this species which they isolated had constants 

 which differed from those of ergosterol; in fact, these workers referred to 

 the sterol as a "chicken provitamin D." Moreover, van Yliet^^ recorded the 

 fact that the activated earthworm pro\atamin D had a potency equal to that 

 of chicken provitamin D. This would not have been the case if it had been 

 ordinary ergosterol. 



The presence of ergosterol has likewise been proved without question in 

 the higher vertebrate forms. Thus, Windaus and Stange'^" noted the pres- 

 ence of ergosterol in the eggs of chickens, although it was believed that 

 this represented an adventitious occurrence, which was to be ascribed to the 

 presence of ergosterol in the feed. A similar explanation has been ad- 

 vanced by Bethke et a/.^""- to explain the presence of vitamin D^ (ac- 

 tivated ergosterol") in hen's eggs, inasmuch as this is not the natural form 

 of vitamin D in this species. In fact, these workers stated that the type of 

 vitamin D present in the tissues and egg-yolks of fowl depended upon 

 whether irradiated ergosterol or cod-liver oil had been the main source of 

 vitamin D in the diet. Variations in the type of vitamin D present in the 

 milk of the cow were also found to be dependent upon the dietary sterol 

 fed."' Although the presence of vitamin D2 in the higher forms may in 

 all probability be traced to the presence of ergosterol in their feed, it is 

 difficult to explain the occurrence of small amounts of vitamin D2 in tuna 

 fish liver oils as recorded by Brockmann and Busse,""* although the vitamin 

 was mainly in the form of vitamin D3 in this case. A possible explanation 

 for the occurrence of ergosterol and vitamin D2 in the tissues and eggs of 

 chickens"^'''^ is the fact that this species can absorb a slight amount of 



'"8 A. G. Boer, J. van Niekerk, E. H. Reerink, and A. van Wijk, U. S. Patent No. 2,- 

 163,659 (June 27, 1939). 



109 A. G. Boer, J. van Niekerk, E. H. Reerink, and A. van Wijk, V. S. Patent No. 2- 

 266,67 1^ (Dec. 16, 1941). 



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



"1 R. M. Bethke, P. R. Record, C. H. Kirk, and D. C. Kennard, Poultry Sci., 15, 

 326-335 (1936). 



"2 R. M. Bethke, P. R. Record, O. H. M. Wilder, and C. H. Kirk, Poultry Sri., 15, 

 336-344 (1936). 



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

 21-30(1936). 



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



1" R. Schonheimer and H. Dam, Z. physiol. Chem., 211, 242-245 (1932). 



ii« W. Menschick and I. H. Page, Z. physiol. Chem., 211, 246-252 (1932). 



