In an introductory historical note the author reviews critically and in chronological order the various attitudes toward the problem of mineral metabolism from the time of Justus von Liebig to the present.
Newer methods of precision have added a large number of minerals to those known to exist in foodstuffs and in the animal organism.
The author points out that we are far from knowing definitely which elements are essential to the life of the animal organism. Not all elements are biogenous.
Little is known of the form in which these biogenous elements occur in nature. Is it immaterial in what form they are introduced, or is their assimilation dependent on a certain form or configuration of the chemical elements?
The organism does not seem capable of reducing an element of a higher stable valence to one of lower value or valence. It is not capable of reducing to more