302 THE VITAMINS 



oil its specificity in rickets. If such prove to be the case, and this factor 

 is regarded as a vitamin, then these results constitute the first dem- 

 onstration of the production of a vitamin in mtro. All that can be 

 deduced at present is that they furnish evidence of the production of 

 an antirachitic factor outside of a living- organism." 



They reported success in activating patent flour and the unsaponifi- 

 able fraction of linseed oil, and the successful storage of activated mate- 

 rial for relatively long periods. Having shown that it is the unsaponifiable 

 fraction of vegetable oils, and not the true fat which is capable of 

 activation, and knowing that the main constituent of the unsaponifiable 

 fraction consists of phytosterol, they next investigated (1924) the 

 possibility of activating such substances by irradiation. They found 

 that 0.25 cubic centimeter of an irradiated 1 per cent suspension of 

 highly purified phytosterol* or 0.1 cubic centimeter of an irradiated 1 

 per cent cholesterol* (m.p. 148.5° C.) fed daily to rats on a rickets- 

 producing diet was protective. "The fact that a well defined chemical 

 substance can be endowed with antirachitic potency by means of irradia- 

 tion is remarkable and of possible physiologic significance. ... As is 

 well known, the epidermal portion of the skin contains a large amount 

 of cholesterol situated in its deeper layers in close approximation to the 

 prickle cells. It would seem quite possible that the cholesterol in the skin 

 is normally activated by ultraviolet irradiation and rendered antirachitic 

 — that the solar rays and similar artificial radiations are able to bring 

 about this conversion. This point of view regards the superficial skin as 

 an organ which reacts to particular light waves (the epidermal organ) 

 rather than as a mere protective covering." . . . "It would be prema- 

 ture to more than suggest this hypothesis of the action of cholesterol in 

 rickets." 



Similar results were reported by Rosenheim and Webster (1925) 

 and by Steenbock and Daniels (1925). 



Hess and Weinstock (1925a) found that 0.1 cubic centimeter of an 

 irradiated 1 per cent suspension of "cholesterol" injected subcutaneously 

 protects against rickets. By the use of light filters they found such 

 cholesterol to be activated by ultra-violet radiations of approximately 

 the same wave lengths as those which had been found to be specific 

 for rickets when animals were subjected to direct irradiation, i.e., rays 

 as short as 289 ^fi or 280 /i/i and between 200 and 290 nn with 90 per 

 cent of rays between 254 fifi and 265 /</i. 



By means of a spectrograph, Macht, Bell and Elvers (1925) studied 



* From later work it appears that such specimens of cholesterol and phytosterol as were 

 accepted as pure at the time of these experiments really contain some ergosterol which, as 

 shown later, is now held to be the substance which yields vitamin D upon irradiation. 



