Bicarbonates, alkali protein compounds and small quantities of alkali phosphates together constitute the alkali reserve of the blood plasma.1 Under normal conditions these substances are present in very constant quantities. A diminution in the alkali reserve is known as acidosis and may be recognized by a variety of clinical symptoms and by characteristic alterations in the composition of the blood, urine and alveolar air.
The alkali reserve maintains the plasma at a constant slightly alkaline reaction, despite the fact that acid products of metabolism are continually being poured into the blood. Chief among the acid products, so far as total quantity is concerned, is carbonic acid. This, as carbon dioxid, enters the plasma circulating through the tissues and is taken up partly in combination and partly as dissolved carbonic acid. An almost infinitesimal change in reaction in the direction of acidity occurs. This slight change is sufficient