332 THE VITAMINS 



He explained his results tentatively, on the theory that the hematopor- 

 phyrin increased remarkably the sensitivity of the organism to rays of 

 light that lie within the visible part of the spectrum. 



Belloc, Fabre, and Simonnet (1930) compared two samples of 

 plankton collected from the same water, one in midsummer and the 

 other in the spring, for their content of ergosterol and vitamin D. The 

 sterols were separated from the material by saponifying the chloroform 

 extract with potassium hydroxide and crystallizing the unsaponifiable 

 fraction from ethyl alcohol, the whole process being conducted rapidly 

 with protection from air and light. The crystallized products were sub- 

 jected to physical (ultra-violet absorption), chemical (the Rosenheim 

 and Meesemaeker color tests), and biological tests (feeding experiments 

 with rats). As judged by these tests, the "summer" plankton contained 

 both ergosterol and vitamin D, while the "spring" plankton gave tests 

 for the provitamin but not the vitamin. Belloc, Fabre, and Simonnet 

 conclude that the biological activity of plankton is a function of a num- 

 ber of factors, prominent among which is light, but that the presence 

 of the antirachitic factor in the food of fish does not exclude the 

 hypothesis of an activating property of certain of their organs or the 

 intervention of light rays. 



Production of Antirachitic Potency in Foods. — Hess and Weinstock 

 (1924, 1925) reported success in conferring antirachitic potency by 

 ultra-violet irradiation upon cottonseed oil, linseed oil, green or etiolated 

 lettuce and young growing wheat plant, and showed that irradiated 

 green wheat plant fed at a 10 gram level (no other level tried) to 

 rats on Diet No. 84 was effective in protection from rickets even after 

 being stored from 3 days to 2 weeks and that activated linseed oil in 

 daily doses as low as 0.1 cubic centimeter was potent after 6 months' 

 storage. Irradiated patent flour fed as 95 per cent of the diet was potent 

 (no other level tried). Also they reported that dry milk (5 per cent of 

 diet), flour and spinach (10 gram level) can be rendered antirachitic 

 by radiations from the quartz-mercury vapor lamp. This potency was 

 maintained by the spinach after it had been boiled one-half hour (10 

 grams daily fed). 



Steenbock and Black (1925) found that lard, olive oil, fresh corn 

 oil, and coconut oil could be activated by irradiation (fed at 2 per cent 

 levels) but old corn, peanut, oleo and coconut oils (kept from 6 to 10 

 years in the laboratory) could not be activated (2 per cent levels fed). 

 They were able to increase the antirachitic potency of whole milk and 

 egg yolk from 15- to 20-fold by irradiation. 



Later Steenbock, Hart, Hoppert and Black (1925) recorded that 



