Vitamins and Antivitamins 37 



performed by an enzyme containing copper. It has also been found 

 that black sheep are unable to grow black wool on a copper- 

 deficient diet, a copper enzyme being the agent of the formation of 

 the black pigment. 



Another not very common metal which is found in many living 

 organisms is molybdenum. It has been found recently that this is 

 required for certain enzyme systems, particularly xanthine oxidase, 

 which is concerned with the breakdown of 'purines' and performs a 

 step in a series of reactions which ultimately leads to their excretion 

 as uric acid. Xanthine oxidase is present in quite appreciable 

 quantities in cows' milk. 



Until recently it was not known in what substances the animals 

 made use of cobalt, but in 1948 two teams of workers, one headed 

 by Dr Lester Smith in England and the other by Dr Rickes in New 

 Jersey, isolated a cobalt-containing substance (sometimes known as 

 vitamin B12 from the liver; this substance ameliorates pernicious 

 anaemia. If the animal is unable to make enough of this substance, 

 red blood cells are not manufactured in the marrow. But injecting 

 sheep with either a cobalt salt or this pernicious anaemia factor, did 

 not cure the deficiency condition. Cobalt taken by the mouth is 

 effective, but not if injected directly into the blood. It was therefore 

 thought that even in cobalt-deficient pastures, sheep get enough 

 cobalt to make the anti-anaemic factor; but insufficient to satisfy the 

 micro-organisms which play so large a part in the digestive apparatus 

 of ruminants. 



How the micro-organisms use cobalt is not known at present; but 

 it may be that they synthesize for their own purposes compounds 

 similar to the pernicious anaemia factor. In fact this substance has 

 been isolated from a mould Streptomyces griseus — the same one 

 which yielded streptomycin. What an astonishing thing ! After years 

 of great effort, scientists succeed in isolating, from liver, the substance 

 which is necessary for the formation of red blood corpuscles in the 

 bone marrow. No sooner is it isolated than it is also discovered as 

 the product of a mould. 



If all this is correct, the emaciation and eventual death of the 

 animals on cobalt-deficient pastures is due to the lack of a milligram 

 or so of cobalt daily, which is apparently required in the enzyme 

 systems of certain micro-organisms, which synthesize vitamins or 

 other substances required by the animal in small amounts. The 

 whole situation rather reminds one of the disastrous consequences 

 of the loss of a nail in the nursery rhyme — but in this case the nail is a 

 cobalt one, which is required as a necessary part of the structure of 

 an essential vitamin. 



