ME. A. H. CHURCH ON TURACIN, AN ANIMAL PIGMENT CONTAINING COPPER. 635 
I do not wish to attach great importance to the above formula for turacin ; but it 
certainly represents the analytical results closely, and possesses, in its atom of copper, 
an element of control similar to that of a metallic salt. In its permanence and its con- 
stancy of composition, turacin is separated widely from complex bodies like the albumi- 
noids, which in many particulars it resembles ; for it must be here noted that the ana- 
lyses above given have been made with different specimens of turacin — some with speci- 
mens from Musophaga violacea , but in most instances with the pigment from the Cory- 
thaix albocristata, or C. porphyreolopha. Notwithstanding this diversity of origin, and 
certain changes in the modes of preparation, the analytical results have been remarkably 
concordant. 
Affinities of Turacin. — In its colour, in its absorption-spectrum, and in some of its 
other characters, turacin corresponds closely with the scarlet cruorin of blood, yet it 
contains no iron, or, at most, an inappreciable trace of this metal. Iron, however, exists 
to the extent of between 6 and 7 per cent, in hsematin, the chief derived colouring- 
matter obtained from blood, and is doubtless a constituent of the original cruorin; yet 
if, in turacin, the iron of cruorin is replaced by copper, there are other and wider differ- 
ences of composition and deportment between the two pigments, which prevent us from 
regarding turacin as a copper cruorin. Moreover turacin does not seem to occur in 
corpuscles, but to be homogeneously distributed in the barbs, barbules, and crochets of 
the red feathers in which it occurs. 
Turacin seems to characterize the closely allied genera Musophaga and Corythaix. 
These birds, though with the other Touracous distinctive of the African Ornis, are not com- 
mon; and in consequence the supply of turacin for experimental purposes is very limited. 
I have not detected it in any of the other red-plumaged birds which I have examined. 
The quantity of turacin in a single bird is small. It is most abundant at the pairing- 
season, and the bridal plumage of a Corythaix albocristata generally yields from two to 
three grains of the pigment. One bird, then, may contain in the colouring-matter of its 
wings nearly - 2 of a grain of metallic copper. 
Turacin is the first animal or vegetable pigment containing copper as an essential 
constituent which has hitherto been isolated ; yet traces of copper have been repeatedly 
found in both animals and plants. It was detected by Harlen in the blood of certain 
Ascidia and Cephalopoda. It occurs in Limulus cy clops. Cancer pagurus , Acanthias zeus , 
and Conger vulgaris, its quantity being in inverse ratio to the quantity of iron pre- 
sent. The blood of Helix pomatia contains much copper, the part of the ash insoluble 
in water yielding 2 - 57 per cent. Many chemists have detected minute traces of 
copper in human blood ; and twenty years ago Deschamps arrived at the conclusion 
that it is normally contained in the blood of man and animals. Odling and Dupre have 
indeed subsequently detected copper in flour, straw, hay, meat, eggs, cheese, and other 
articles of food. It has been supposed that the copper detected in some of these sub- 
stances has been introduced in the course of analysis by the use of brass burners and 
retort rings ; but these in most cases are a purely imaginary source of error. It is not 
