II 
THE PIGMENTS OF ORGANISMS 
49 
modern chemistry, and have heard of the wonderful 
discoveries as to the composition of the sun and 
some of the stars which have followed from the 
spectroscopic examination of the light emitted by 
these bodies. Now we have already seen that 
many of the pigments of plants and animals are 
extremely fugitive and unstable, many of them also 
are exceedingly difficult to extract from the tissues. 
By means of the spectroscope, however, the coloured 
tissues may often themselves be directly examined, 
and on account of the readiness with which the 
operation may be performed, a large number of 
pigments are known chiefly by their spectra. Now 
even in the case of the metals, we find an authority 
like Mr. Crookes saying that “ inferences drawn from 
spectrum analysis per se are liable to grave doubt, 
unless at every step the spectroscopist goes hand in 
hand with the chemist.” If this be true of radiant 
matter spectroscopy, where the spectra are capable 
of extraordinarily accurate study, how much more 
likely is it to be applicable to the spectrum analysis 
of pigments, where the methods are as yet clumsy 
and inadequate! Thus we find as a matter of 
practical experience, that it has been found impos¬ 
sible in the aniline industry to employ the spectra 
as a test for affinity. Again, in spite of the 
common assertion that pigments yielding identical 
spectra are themselves identical, we find that three 
distinct pigments—haemoglobin, carmine, and turacin 
—are described by competent authorities as giving 
spectra which are virtually identical. Turacin, a 
pigment discovered by Professor Church, is of 
purplish-violet colour, and occurs in the feathers of 
E 
