COLOUR 95 
Angl. p. 393) quoted from both, and thus the word came into 
English use, even to finding its way into an Act of Parliament 
(43 and 44 Vict. cap. 35). In the Mexican language it was variously 
compounded, as Ococolin (Mountain-Partridge), Acolin (Water-Quail), 
and Cacacolin (cf. Hernandez, op. cit. pp. 32, 42). These have not 
all been determined ; but it is generally agreed that Colin alone 
meant some species of the genus Ortya. 
COLOUR, as perceived in the various parts of Birds, is produced 
by pigment or by structure or by a combination of the two. Three 
classes of colours can therefore be distinguished. 
I. The so-called chemical or absorption colours are always due to 
colouring matter, which may exist in the form of a solution dif- 
fused in the coloured parts, or in the form of pigmented corpuscles, 
distributed in and between the cells of the various organs. Such 
colours do not vary or change under any position of the light or 
eye; and even under transmitted light a red, yellow, brown, or 
black feather will always appear the same. Black, red, and brown 
always belong hereto, orange and yellow mostly, but rarely green, 
and never blue. 
The principal colour pigments are :— 
Zoomelanin, the black animal colouring matter, distributed in 
amorphous little corpuscles, insoluble in Water, Alcohol, Acids, 
or Ether, but dissolved and destroyed when boiled in Caustic 
Potash and then treated with Chlor; it consists of about 53°5% 
of Carbon, 4°6 of Hydrogen, 8:2 of Nitrogen, and 33-7 of Oxygen. 
Zoonerythrin, red, hitherto found in the red feathers of Cotinga, 
Pheenicopterus, Ibis, Cacatua, Cardinalis, and others, and in the 
“rose” round the eyes of the Tetraonide. It is soluble in Ether, 
Alcohol, and Chloroform, but not in Acids or in Potash ; the variable 
amount of fat or oil in the feathers of the Flamingo causes them 
to be more or less intensely coloured. 
Zooxanthin, yellow, can be extracted by boiling in absolute 
Alcohol, and is a diffused pigment which tinges the shafts, rami, 
and radii of the feathers, and is possibly the same in the yellow 
feet and bills of Birds-of-Prey and Anseres. Like Zoonerythrin 
it is a coloured fatty oil. 
Turacin is a most peculiar pigment, discovered by Church in 1867 
(Phil. Trans. 1869, pp. 627-636) in the red feathers of the Muso- 
phagide, and seems to be restricted to these birds. It consists of the 
same elements as Zoomelanin with the addition of from 5 to 8Z of 
copper. It can easily be extracted by weak alkaline solutions, such as 
Ammonia, and with the addition of Acetic Acid, it can be filtered off 
as a metallic red or blue powder. The presence of metallic copper 
is indicated by the green flame of the red feathers when burnt. 
These birds lose the red colour when washed by the rain, but regain 
