The trace elements: A new chapter in nutrition.

Formerly reported by analysts as being present as "traces", the minute amounts of many elements present in plant and animal materials can now be detected and estimated with a remarkable degree of sensitivity and accuracy. Some of this heterogenous group of metals and nonmetals have been shown to be essential for life or for the well-being of animals, including man; others possess toxic properties, while yet others are probably there as contaminants. Although present in such extremely small quantities, those known to be essential play highly individualistic as well as astonishingly varied roles in our metabolic processes; they must, therefore, take their place with the other nutrients needed in our diet.