76 COMPARATIVE PHYSIOLOGY 



blue tinge. Reduced haemocyanin does not show any absorp- 

 tion bands. The spectrum of oxyhaemocyanin from molluscs 

 and arthropods shows one band in the yellow and the beginning 

 of another in the blue in virtue of the copper-pynol complex 

 in the haemocyanin molecule. The position of the yellow 

 band in molluscs is about A579/X/X, and in Crustacea about 

 A563/X/X. 



As regards the properties of haemocyanin as a respiratory 

 pigment, Dhere finds that oxy-haemocyanin of both Crustacea 



D/ssccfstion Curves oF Haemocydnin In CrustdCesn Blood. 



Oxygen Tension 



10 40 60 80 /CO 120 ItO 160 ISO 200 220 2iO 260 280 3C0 3:0 3'tO 366 



Fig. 1 8. — (After Stedman and Stedman.) 



and molluscs undergoes dissociation by lowering of the oxygen 

 tension, exposure to an inert gas or heating. There is no 

 combination between carbon monoxide and haemocyanin, 

 which however (snail, lobster) form a green compound with 

 N2O2. The physiological role of haemocyanin in the respira- 

 tory processes of Crustacea and molluscs is not completely 

 established ; but is strongly suggested by comparison of the 

 haemocyanin content (as measured by the amount of copper 

 present) with the oxygen capacity of the blood in different 



