Abstract
ABOUT 100 years ago Claude Bernard pointed out that the true environment of the body is the interstitial fluid which circulates slowly through the tissue interstices, bringing to the cells their nutriments and removing from them their wastes.1 This fluid is somewhat akin in composition to dilute sea water, having in common with it a balanced salt composition and a blandly alkaline reaction. Indeed it is probable that it mirrors the composition of the sea at that time in the prehistoric past when our Cambrian ancestors first found it advantageous to enclose a bit of the sea within their integument and to make it an intimate part of themselves.2 This interstitial fluid, like sea water, contains sodium bicarbonate and dissolved carbon dioxide or carbonic acid. These two components, one basic and one acidic, constitute a buffer mixture. Together they stabilize the reaction or hydrogen ion concentration of the

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