26 
COLOUR IN NATURE 
CHAP. 
purple from various small shell-fish, such as Murex 
and Purpura, while the different preparations of 
carmine and cochineal, saffron, and hsematoxylin or 
logwood are other familiar examples of pigments 
produced by animals or plants which are habitually 
employed as colouring-agents. The greater number 
of the pigments of plants and animals are, however, 
too fugitive to be so utilised, and in consequence are 
in their pure state unfamiliar to most people. Such 
are chlorophyll itself, the blue, red, orange and 
yellow pigments of flowers, and the green, red, 
yellow and orange pigments of animals, most of 
which are destroyed by light or other agents with 
great rapidity. It is indeed worth noting that most 
of the natural dyes are of vegetable origin, and that 
they are usually inconspicuous and apparently unim¬ 
portant during the life of the plant, cf. haema- 
toxylin, brasilin, etc. So, too, when they are of 
animal origin, they are not usually important in 
producing the coloration of the living creature, cf. 
Murex, the coccus insect, etc. It is partly in con¬ 
sequence of the fact that the pigments important 
in producing coloration are so fugitive and so 
difficult to obtain in a pure state, that so little is 
really known of their relations and constitution. 
Many of them, indeed, have hardly been investigated 
at all. 
We may note here a point which will be dwelt 
on in detail in its proper place, that a pigment 
found in an animal need not necessarily be formed 
by that animal. There are some instances of 
pigments which are transferred from one animal 
or plant to the tissues of another by the food with 
