VITAMINS 93 



then be compared with those occiirriniv in certain diseases of 

 man. A frequent practice in medicine is tiie administration of 

 gland extracts in the case of deficiency, and removal of parts 

 of olands which have been secretino- to excess. 



But even if the food an animal eats is of the riohl (juantity 

 and quality it will not be assimilated unless certain obscure 

 ingredients known as Vitamins are present. Nobody has 

 succeeded in isolating a vitamin, though as knowledge has 

 increased we have been able to get them in more and more 

 concentrated forms. You can go into the chemist's shop and 

 ask, as the lady did, for "half a pound of pure vitamins," 

 but the chemist will be unable to supply you. In some way 

 these unknown bodies exercise some control over nutrition. 

 Without one form of vitamins children will not grow. The 

 absence of another leads to scurvy in adults and children. 

 Scurvy, which plays so great a part in pirate stories and in 

 the narratives of Polar explorers, has for a long time been 

 treated by administering fresh vegetables and lemon- juice or 

 fruit, and it is these fresh foods which supply the vitamins. 

 Some authorities associate the disease of rickets so common 

 in childhood with an absence of vitamins, and much work 

 on this subject has been and is being done since the war 

 amongst the starving children of Vienna. Rickets can be 

 cured by supplying the child with vitamins or by exposing 

 it to the sun-light or ultra-violet rays; whether the rays cure 

 of themselves or whether they promote the welfare of the 

 vitamins is not yet clear. 



Vitamins are classified as: 



Vitamin A (Fat Soluble). 



Vitamin B (Water Soluble). 



Vitamin C (Water Soluble or Anti-Scorbutic). 



It has recently been shown that Vitamin A — which is 

 possibly identical with the yellow pigment carotin — is 

 "activated" by sunlight. 



The chemical composition of vitamins is not known. They 

 exist in extremely small quantities in various foods and cannot, 

 as far as is at present known, be synthesized by animals. The 

 animal is dependent upon the plant for them. It seems that 

 their formation may be dependent on the photosynthetic 



