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MELANINS. 843
true of the melanoids produced from proteins on cleavage with acids
(Samuely !
)
—yield indol or skatol and a pyrrol substance on fusion
with alkali, while hippomelanin, according to v. Furth and Jebubalem,
gives a fecal odor on this treatment, but does not yield any indol or skatol.
More characteristic than the two last mentioned bodies is a phenol-like
substance, which occurs to a slight extent, and gives a bluish-black
color with ferric chloride (v. Furth).
The cyclic complexes of the proteins are rightly considered as the
mother-substance of the melanins (Samuely and v. Furth and others),
and this view has received support by the behavior of tyrosine with
oxidases. It has been found that by the action of. a plant oxidase,
Bertrand’s tyrosinase,2
upon tyrosine, colored products and then
melanin-like substances are formed, v. Furth with Schneider and
Pribram, Gessard, Neuberg, Dewitz and others 3
have shown that
similar-acting tyrosinases also occur in the animal kingdom, in insects
and sepia, in melanotic tumors and in pigmented skin, and v. Furth
and Jerusalem have prepared an artificial melanin from tyrosine which
shows great similarity to hippomelanin. Finally Neuberg and Jager 4
have also prepared extracts from melanotic growths which formed a dark-
brown pigment from adrenalin. As indicated above, we tend more and
more to accept the view that the melanins are derived from the cyclic
components of the proteins.
In addition to the coloring matters of the human skin it is in place here to
treat of the pigments found in the skin or epidermal formation of animals.
The beautiful color of the feathers of many birds depends in certain cases on
purely physical causes (interference-phenomena), but in other cases on coloring
matters of various kinds. Such a coloring matter is the amorphous reddish-
violet turacin, which contains 7 per cent copper and whose spectrum is very similar
to that of oxyhemoglobin. It must be remarked that according to Laidlaw 5
turacin or at least a pigment with the same properties can be obtained on boiling
lurmatoporphyrin in dilute ammonia with ammoniacal copper solution. Kruken-
berg 6
found a large number of coloring matters in bird’s feathers, namely zooery-
thnn, zoofulrin turacoverdin, zoorubin psittacofulvin, and others which cannot be
enumerated here.
Tetronerythrin, so named by Wurm, is a red amorphous pigment which is
soluble in alcohol and ether, and which occurs in the red warty spots over the eyes
of the heathcock and the grouse, and which is very widely spread among the
invertebrates (Halliburton, De Merejkowski MacMunn). Besides tetronery-
1
Hofmeister’s Beitrage, 2.
2
Compt. Rend., 122.
3
The literature can be found in v. Furth and Jerusalem, Hofmeister’s Beitrage,
10.
4
Neuberg, Virchow’s Arch., 192; Jager, ibid., 198.
6
Journ. of Physiol., 31.
s
Vergleichende physiol. Studien, Abth. 5, and (2. Reihe) Abth. 1, 151, Abth. 2, 1,
and Abth. 3, 128.
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