"
An etiolated earth would be hardly worth living in.
The chlorophyll of the leaves and the hemoglobin of the blood are
similar in constitution. Chlorophyll contains magnesium in place of iron
but iron is necessary to its formation. We all know how pale a plant
gets if its soil is short of iron. It is the iron in the leaves that
enables the plants to store up the energy of the sunshine for their own
use and ours. It is the iron in our blood that enables us to get the
iron out of iron rust and make it into machines to supplement our feeble
hands. Iron is for us internally the carrier of energy, just as in the
form of a trolley wire or of a third rail it conveys power to the
electric car. Withdraw the iron from the blood as indicated by the
pallor of the cheeks, and we become weak, faint and finally die. If the
amount of iron in the blood gets too small the disease germs that are
always attacking us are no longer destroyed, but multiply without check
and conquer us. When the iron ceases to work efficiently we are killed
by the poison we ourselves generate.
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