Mineral metabolism 



15 



This title is broadly interpreted to cover all the biochemical relation- 

 ships of the metallic elements but is specifically restricted to animals in 

 this chapter. In addition, certain non-metals are essential to animals 

 and except for hydrogen, oxygen, carbon, and nitrogen these are dis- 

 cussed here too. The four elements excepted are separately covered 

 in the chapters on the metabolism of carbohydrates, lipides, and 

 proteins. These same chapters deal with the general metabolism of 

 sulfur except for certain special problems of sulfate taken up below. 



NUTRITION 



The various ions believed to be essential for a variety of the higher 

 members of the animal kingdom are taken up in alphabetical order. 

 This sequence is chosen because one cannot assign degrees of require- 

 ment to the elements concerned. Obviously the concept of essentiality 

 means that complete deprivation leads to death and partial defi- 

 ciencies to physiological impairment. Experiment supports this basic 

 concept. 



Naturally the information available differs in quantity and diversity 

 for the different elements. This situation has arisen from the personal 

 interests and prejudices of investigators, accidental factors, availabil- 

 ity of basic biological and chemical knowledge, existence of suitable 

 apparatus and procedural techniques, lack of ideas in some cases, and 

 differences in innate investigational difficulties. One cannot conclude 



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