Lxxxi. Haemocyanin. Part I. the Dissociation Curves of the Oxyhaemo- Cyanin in the Blood of Some Decapod Crustacea

THE blue colour of the blood of certain arthropods and molluscs is due to the presence of a protein, containing copper, which exists in oxidised and reduced forms; the former, oxyhaemocyanin, has a blue colour, whilst the latter, haemocyanin, is colourless. The transformation of the oxidised into the reduced form is readily accomplished by exposing blood containing oxyhaemocyanin to a vacuum or by saturating it with an inert gas; the reverse change takes place spontaneously on again bringing the blood into contact with air. Oxyhaemocyanin has been isolated in crystalline condition from the blood of certain species. [For bibliography see Dhere, 1915.] The properties of haemocyanin immediately suggest that this pigment exercises respiratory functions analogous to those of haemoglobin. This view has, in fact, been almost generally accepted and has received support from determinations, by various authors, of the oxygen capacities of the bloods of a number of marine invertebrates. In the case of those species which contain haemocyanin, the values obtained, although differing widely from species to species and even from individual to individual of the same species, were considerably higher than the oxygen capacity of the sea-water in which the animals lived. With those species containing no haemocyanin, on the other hand, the values approximated to that of sea-water. This is illustrated by the following figures, which are quoted from Winterstein [1909].