CHAP. II.] THE BLOOD. 133 



The Blue Blood of the Octopus. Haemocyanin. 



However interesting the above facts may have been as 

 rendering it most probable that the blue colouring matter of the 

 blood of certain of the Mollusca is concerned in the function of 

 respiration, and suggestive of the possibility that other metals may 

 take the place of iron as constituents of the blood-colouring matter, 

 they are infinitely less important than the observations of Frederique 

 made upon the blood of the Octopus. 



Kabuteau and Papillon 1 had described the blood of the Octopus, 

 and had correctly pointed out that it becomes blue on exposure to air, 

 doubtless in consequence of the action of oxygen. Their researches 

 have been continued by Le*on Frederique 2 with the following most 

 interesting results : 



The blood of the Octopus has a specific gravity of 1047, and it 

 contains between 13 and 14 per cent, of solid matters. The blood 

 contained in the vessels going to the branchiae is colourless, whilst 

 the blood leaving them is of a deep blue colour. If a large artery 

 be exposed in a living octopus, whilst it is immersed in water, and 

 breathing freely, it will be seen to have a deep blue colour, due 

 to a substance dissolved in the plasma ; if the animal be now with- 

 drawn from the water, as the respiration becomes impaired, the colour of 

 the artery is seen to become lighter and lighter, its contents becoming 

 ultimately colourless. 



The blue blood drawn from an artery, if placed in a closed vessel, 

 undergoes, after some hours, a process of bleaching, the change of 

 colour being analogous to the change of the tint of arterial blood 

 when it is similarly treated. When the blue blood is boiled in the 

 receiver of a mercurial pump the blue colour disappears. The same 

 result follows when it is subjected to a stream of H 2 S or C0 2 . 



The blue colour is due to a body to which Frederique has given 

 the name of HAEMOCYANIN. 



This body, like haemoglobin, is allied to the proteids, but still 

 more complex, seeing that it yields a proteid substance as one of its 

 decomposition products, but in addition a colouring matter. In the 

 case of haemocyanin this colouring matter is blue, and contains 

 copper. Following the analogy of haemoglobin the blue compound 

 might be termed oxy-haemocyanin, and the colourless derivative 

 simply haemocyanin. 



Solutions of oxy -haemocyanin when examined with the spectro- 

 scope do not present any 'definite absorption-bands. Solutions of 

 the body, when heated, exhibit slight opalescence at 65 C., and this 



1 Kabuteau et Papillon, "Observations sur quelques liquides, &c." Comptes 

 Rendus, v. 77, (14 Juillet, 1873) p. 137. 



2 L6on Frederique, " Sur 1'organisation et la physiologie du Poulpe." Extrait des 

 Bulletins de V Academic Roy ale de BeJgique. 2 me serie, T. XLVI. N 11 ; 1878. 



