Haem`a*cy"a*nin (?), n. [Haema- + Gr. a dark blue substance.] Physiol. Chem.
A substance found in the blood of the octopus, which gives to it its blue color.
⇒ When deprived of oxygen it is colorless, but becomes quickly blue in contact with oxygen, and is then generally called oxyhaemacyanin. A similar blue coloring matter has been detected in small quantity in the blood of other animals and in the bile.
© Webster 1913.