XIV 
ORIGIN OF PIGMENTS 
291 
haemoglobin of the blood, and that, therefore, its 
amount is a direct measure of the rapidity of the 
degenerative changes occurring in the haemoglobin. 
From some recent work it would, however, appear 
that there is not this direct relation between the 
pigment and haemoglobin. Drs. John Abel and 
Walter Davis, in the course of a laborious investiga¬ 
tion on the pigments of the negro’s skin and hair, 
found that the pigment granules of the epidermal 
cells contained a substratum of non-pigmentary 
substance, apparently of the nature of a highly 
resistant proteid. When this proteid is removed the 
pigment is readily soluble in dilute alkalies, from 
which it may be precipitated by acids. It contains 
carbon, nitrogen, oxygen, hydrogen, and sulphur, but 
in the pure state very little iron. It is the presence 
of sulphur without any considerable amount of iron 
which, in the opinion of the authors, makes an origin 
from haemoglobin very doubtful. The proteid which 
is also present in the pigment granules contains a 
considerable amount of iron as well as of other in¬ 
organic constituents. Floyd showed in 1876 ( Chem . 
News , vol. xxxiv. p. 179) that the skin of the negro 
contains about twice as much iron as the white skin, 
but this is apparently due to the proteid and not 
to the actual pigment itself. The investigators are 
of opinion that the pigment originates from some 
proteid of the blood or “ parenchymatous juices.” 
Similarly Dr. Sheridan Delepine considers that 
melanin is elaborated out of the plasma of the blood 
and is not a derivative of haemoglobin. On the 
other hand, he is of opinion that haemoglobin itself 
is perhaps manufactured from some “ antecedent, 
