from
The Collaborative International Dictionary of English v.0.48
Haemacyanin \H[ae]m`a*cy"a*nin\ (-s[imac]"[.a]*n[i^]n), n.
[H[ae]ma- + Gr. ky`anos a dark blue substance.] (Physiol.
Chem.)
A substance found in the blood of the octopus, which gives to
it its blue color.
[1913 Webster]
Note: When deprived of oxygen it is colorless, but becomes
quickly blue in contact with oxygen, and is then
generally called oxyh[ae]macyanin. A similar blue
coloring matter has been detected in small quantity in
the blood of other animals and in the bile.
[1913 Webster]