"The record of the rocks contains very little, other than bacteria and one-celled plants until, about a billion years ago, after some three billion years of invisible progress, a major breakthrough occurred. The first many-celled creatures appeared on earth."

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It has occurred to me that possibly the white corpuscles may have the office of picking up and digesting bacterial organisms when by any means they find their way into the blood. The propensity exhibited by the leukocytes for picking up inorganic granules is well known, and that they may be able not only to pick up but to assimilate, and so dispose of, the bacteria which come in their way does not seem to me very improbable in view of the fact that amoebae, which resemble them so closely, feed upon bacteria and similar organisms.

— George Miller Sternberg