The Respiratory Proteins of the Blood

Although the buffer action of the blood of man has received most thoroughgoing analysis (Van Slyke, 1921) the similar phenomena in the body fluids of invertebrates have been described only in such a way as to define the magnitude of the problem without at all adequately contributing to its solution. Quagliariello (1916) showed that relatively large amounts of acid or alkali must be added to the blood of certain invertebrates in order to produce a given change in its reaction. Thus in the cephalopods, Eledone and Octopus, some 200 mg. of sodium hydroxide were required to bring the reaction of a liter of blood from its normal vaIue of pH 7.36 or 7.54 to pH 9.0. In the case of the horseshoe crab, fimulus polyphemus, we find that 400 mg. of sodium hydroxide are required to produce this effect. This is 1000 times the amount required to produce a comparable effect in distilled water. To what components of the blood is this large buffer effect due? Parsons and Parsons (1923-24) amplified the observations of Quagliariello by working out the carbon dioxide dissociation curves of a number of marine invertebrates. They point out that those bloods which combine with carbon dioxide in quantity are rich in hemocyanin. On the other hand Nitzescu and Cosma (1927) conclude from a study of the carbon dioxide dissociation curve of the snail, Helix pomatia, that in this species protein substances (hemocyanin) do not play the principal r81e in the acid-base equilibrium. Redfield, Coolidge, and Hurd (1926)