APPENDIX B 663 



vitamin, hence the importance of sufficient sunlight, the ultra-violet rays 

 in which transform any inactive " provitamin " present in the body into 

 the active vitamin. 



Certain eye-troubles (such as night-blindness) and an unhealthy con- 

 dition of the mucous membranes result from a deficiency of " Vitamin A ". 

 This vitamin is readily obtained from fresh green vegetables (e.g. spinach 

 or cabbage) and from yellow root vegetables (e.g. carrot), in fact from all 

 foods rich in the chromatophore pigment carotene, which is the provita- 

 min. The vitamin is also present in fish-liver oils and in ox-liver. In 

 this case the provitamin is synthesised solely by plants ; the transfor- 

 mation of carotene into the active vitamin, on the other hand, takes 

 place so far as is known only within the animal body. 



Other serious diseases due to vitamin deficiency, but less familiar in 

 Europe, are ' beri-beri " ("Vitamin B ± " deficiency) and "pellagra" 

 (deficiency of the " P.P. Vitamin "). 



At the time when the vitamin theory of deficiency diseases was first 

 put forward (19 12) and for many years afterwards, little or nothing was 

 known about the chemical nature of vitamins, which were indeed long 

 regarded as mysterious if not as miraculous agents. More recently, 

 however, most of them have been isolated in the pure state, analysed 

 and their constitution determined ; several have even been synthesised. 

 It has already been noted that " Vitamin A" is a derivative of the com- 

 plex hydrocarbon carotene. " Vitamin C " is ascorbic acid, C 6 H 8 6 and 

 ' Vitamin D " is a modification, under the influence' of ultra-violet 

 radiation, of ergosterol, C 28 H 44 0. 



We are, in fact, now in a position to administer all the principal 

 vitamins in the pure form as curative or preventive agents, if need be. 

 The first line of defence against deficiency diseases, however, should be 

 a good mixed diet, including daily supplies of fresh vegetables and 

 fruit ; in addition, ample sunlight is essential, or, where sunlight is 

 deficient, regular doses of cod-liver or halibut oil. 



