308 W. I. Card and I. N. Marks 



does in animals, but the state we observed bore no resemblance 

 to low calcium tetany as seen clinically. 



The other point worth discussing is the level of depletion at 

 which these symptoms appeared. It seems likely from this 

 one case, and we have failed to find a comparable example in 

 the literature, that symptoms of what might be called moder- 

 ate severity appeared when something like 25-30 per cent 

 depletion of the total body magnesium had occurred. If we 

 may adduce evidence from animal experimental work, 

 Blaxter, Rook and MacDonald (1954) calculated that in 

 calves on magnesium-deficient diets symptoms appeared when 

 a deficit of about 25-30 per cent magnesium had occurred, 

 while at death it was estimated that 35 per cent of the magnes- 

 ium in the body was lacking. If this general conclusion is 

 true, it follows that the small deficits of 50-100 m-equiv., 

 which have been described by various authors (Nabarro, 

 Spencer and Stowers, 1952), are unlikely to produce clinical 

 manifestations and in themselves hardly call for treatment. 

 In man, the conditions necessary to produce magnesium 

 depletion sufficiently severe to result in a recognizable clinical 

 state are unusual and can hardly be expected to occur with 

 any frequency. 



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