NOTES AND MEMORANDA. 165 



asphyxiated tint. The same takes place if the respiratory muscles 

 are paralyzed by the section of the pallial nerves. 



Haemocyauin appears to be the only albuminoid substance in the 

 blood, as is proved by the method of successive coagulations by heat. 

 It is easy to isolate ; being the only colloid substance in the blood, it 

 is sufficient to subject the plasma of the blood to an energetic dialysis 

 for three or four days so as to eliminate completely the salts and 

 other diffusible substances. The liquid is then filtered and evapo- 

 rated at a low temperature, when a blue brilliant substance is obtained 

 in appearance like gelatine. It becomes blue in contact with oxygen, 

 but colourless in a vacuum ; coagulates in clots by heat, alcohol, ether, 

 tannin, the mineral acids, and the gi'eater part of the salts of the heavy 

 metals. It burns with an odour of burnt horn and leaves a residue so 

 rich in copper, that the blowpipe at once establishes its presence. 



The copper seems to be in the same state as the iron in haemo- 

 globin and it plays an analogous part. Hfemogiobin may as is 

 known be decomposed into ferriferous hasmatin and a coagulated 

 albuminoid substance not containing iron. Haemocyanin gives the 

 same reaction. M. Fredericq has not yet been able to determine 

 the proportion of copper or the proportion of oxygen with which it 

 combines. 



Chromatic Function in the Octopus. — M. Fredericq also finds * 

 that the changes of colour in the skin of the octopus do not generally 

 correspond to mimetic facts, but might rather be classed with the 

 changes which the vasomotors produce in the human face. They 

 express the different emotions, especially anger or fear. 



A quick movement made before an octopus quietly breathing in 

 the aquarium, renders a black spot immediately visible on the two 

 extremities of the pupil, which dilates. The phenomenon disappears 

 almost as quickly as it appeared. If the animal is excited still 

 further, it gets into a great fury ; its whole body assumes a dark 

 colour, and the papillfe of its back bristle up. These changes of 

 colour depend upon the central nervous system. The section of the 

 nerve which goes to the muscles of the chromatophores is enough to 

 paralyze the latter, and to bring on the passive phase of withdrawal of 

 the chromatophores. That part of the skin served by the nerve 

 immediately becomes pale, and then presents the minimum of colora- 

 tion. 



The excitation of the peripheral end of the nerve cut has precisely 

 the contrary effect. In this case, all the chromatophores which depend 

 upon it are brought into the condition of expansion, in consequence of 

 the contraction of the radiating muscles ; and the corresponding part 

 of the affected surface presents the maximum of coloration. 



Owing to their superficial situation and extended distribution, the 

 pallial nerves are extremely well adapted for the demonstration of 

 these facts. 



In the normal state, the octopus generally presents a tint of 

 medium intensity ; the dilator muscles of its chromatophores are in a 



* ' Comptes Rendus,' vol. Ixxxvii. (1878) p. 1042. 



