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HISTIDINE. 159
the behavior of indol and skatol with the aromatic aldehydes have been
carried out by Blumenthal. 1
For the detection of indol and skatol in, and their preparation from,
faeces and putrefying mixture-, the main points of the usual method are
as follows: The mixture is distilled after acidifying with acetic acid;
the distillate is then treated with alkali (to combine with any phenols
which may lie present) and again distilled. From this second distillate
the two bodies, after the addition of hydrochloric acid, are precipitated
by picric acid. The precipitated picrate is then distilled with ammonia.
The two bodies are obtained from the distillate by repeated shaking
with ether and evaporation of the several ethereal extracts. The residue,
containing indol and skatol, is dissolved in a very small quantity of
absolute alcohol and treated with 8-10 vols, of water. Skatol is precip-
itated, but not the indol. The further treatment necessary for their
separation and purification will be found in other works. 2
Skatosine, GoHieNoOo, is a base first obtained by Baum in the pancreas auto-
digestion and later studied by Swain. It develops an indol- or skatol-like odor
on fusing with potassium hydroxide. Langstein 3
obtained a substance which is
perhaps identical with skatosine, in the very lengthy peptic digestion of blood
proteins. ’
/-Histidine, C6H9X3O2, is j3-imidazol-a-aminopropionic 4
CH-NHX
C N^CH
acid, =CHo
CH(NH2)
COOH
Histidine was first discovered by Kossel in the cleavage products
of sturine. It was found at the same time by Hedin in the cleavage
products of proteins by acid hydrolysis, and by Kutscher among the
products of tryptic digestion, and finally also as a cleavage product of
many different animal and plant protein substances. It does not occur
in the protamines, with the exception of sturine. Of the protein bodies
globin (from horse-haemoglobin) seems to be richest in histidine, as
’Sasaki, Bioch. Zeitschr. 23, 29; Deniges, Compt. rend. soc. biol., 64; Blumenthal,
Bioch. Zeitschr., 19.
2
For quantitative, colorimetric determinations of indol in feces see Einhorn and
Hiibner, Salkowski’s Festschrift, Berlin, 1904; C. A. Herter and Foster, Journ. of
biol. Chem., 2.
3
Baum, Hofmesister’s Beitrage, 3; Swain, ibid.; Langstein, see Hofmeister, Ueber
Bau und Gruppierung der Eiweisskorper, in Ergebnisse der Physiologie, I, Abt. 1,
1902.
1
Sec Pauly, Zeitschr. f. physiol. Chem., 42; Knoop and Windaus, Hofmeister’s
Beitrage, 7 and 8; Knoop, ibid., 10; Ackermann, Zeitschr. f. physiol. Chem., 65.
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