358 



ANIMAL BIOCHEMISTRY 



preventing vitamin production by irradiation of the skin. Within the 

 generation it has been reported that in northern China 2 to 5 per cent 

 of pregnant women die in labor from the adult form of rickets. 



Among children severe rickets is still common in many areas, and 

 mild rickets was demonstrated in almost half of the 700 children dying 

 of all causes in Johns Hopkins Hospital in 1940 to 1942. In England 

 as late as 1920 there were 1,760 children in elementary school with 

 rickets of crippling degree. Even in 1944 there were estimated to be 

 24,000 cases of mild rickets in Great Britain in children under a year 

 old. Fortunately these symptoms had largely disappeared when the 

 children became older. Although still a problem even in the West, 

 this disease is not so common as it once was. In 1868 one-third of all 

 London children had severe rickets. Most of the others probably had 

 mild cases. 



Rickets is most j^revalent where climate or custom prevents ex- 

 posure to the sun. Crowded urban and heavily industrialized northern 

 areas in the winter months tend to produce the greatest need for 

 dietary vitamin D. Excejit in fish this vitamin is not stored so exten- 

 sively as is vitamin A. Apparently at least weekly supplies of D are 

 needed. 



VITAMIN E 



At least 40 nattnal and synthetic compounds are known to have 

 some activity as replacements for a-tocopherol, the most abundant 

 and one of the most effective forms of vitamin E. Three other 

 tocopherols have been isolated, all with high vitamin activities. 



CH3- 

 HO- 



CH3 CH3 



CH. 



CHs CH3 CH3 



1 I 1 



(CHo)3CH(CH2)3CH(CH2)3CH 



CH3 



a-tocopherol 



HO 



CH3 



/3-tocopherol 



