AN ANIMAL PIGMENT CONTAINING COPPER. 
513 
ich leider erst zu einer Zeit bekannt geworden bin, wo diese Untersuchungen bereits 
abgeschlossen waren und ausgearbeitet vorlagen, theilt Church Folgendes rnit : 
* Turacin, by long exposure to air and moisture, or by continued ebullition with water 
or alkaline liquids, acquires a colour closely resembling that of chlorophyll.’ ’ 
Dr. Krukenberg decides, after comparing the spectrum of altered turacin, as given 
in my memoir (loc. cit., fig. 4), with the spectrum of turacoverdin, that the presence 
of the absorption band on the less refrangible side of line D indicates the presence of 
his turacoverdin in my “altered turacin,” and proves that I had, in 1869, 
transformed turacin into turacoverdin, although there remained, as I had at the 
time conjectured, some unaltered turacin in the preparation examined. Although I 
cannot but appreciate very highly the handsome way in which Dr. Krukenberg 
speaks of my work and bis confirmation of my results, I am unable to agree with 
Mr. F. E. Beddard* * * § when he states that Dr. Krukenberg has added important 
details to those furnished by its discoverer with regard to turacin. And I may add 
in this place the remark that, if turacin be transformable in the way above described 
into turacoverdin, it is impossible that the latter can contain as essential elements 
either iron or manganese. 
The numerous observations which have been made from time to time as to the 
occurrence of copper in certain Mollusks and Arthropods have finally resulted in the 
detection of a definite cupreous pigment in the blood of certain members of these two 
groups. This body exists in two states, and possesses, like haemoglobin, respiratory 
functions : oxidized it is blue, but in the reduced condition colourless. Its spectrum 
has no definite absorption bands. It was named haemocyanin by Leon Fredericq,! 
to whom we owe some admirable researches on this important compound. It has 
been recognised in several genera of Crustacea, of Arachnida, of Gastropoda, and of 
Cephalopoda. It is a coagulable proteid belonging to the globulin group, and 
contains a very small proportion of copper—a proportion which may be just high 
enough to be comparable with the proportion of iron present in haemoglobin.J 
Haemocyanin is thus widely removed by its chemical and physical characters, as well 
as by its physiological role, from turacin. It is a far less stable body, and contains a 
comparatively insignificant percentage of the characteristic metallic element. It 
would, I think, be desirable to learn if there could be obtained from haemocyanin a 
cupreous derivative bearing to its source a relation analogous with that borne by 
haematin to haemoglobin. At present, haemocyanin and turacin are the only definite 
animal pigments containing copper which have been recognised. 
In this place reference may be made to a letter§ on the subject of copper in Birds 
* 1 Nature,’ December 19, 1889. 
f ‘Bulletin de l’Academie Royale de Belgique,’ 2 nie serie, vol. 46 (1878). 
+ [P. Heim bas recently (‘ Comptes Rendus,’ vol. 114, pp. 771-4) controverted several of the statements 
made by Bredericq as to the composition and properties of hasmocyanin; he denies that copper is an 
essential constituent of this compound.—Postscript, September 1, 1892.] 
§ ‘ Chemical News,’ vol. 28, p. 212. 
MDCCCXCII.—A. 3 U 
