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PROTAGON. 607
are, therefore, as are Lesem, Thudichum, WdBNEB and Thierfelder,1
and others, of the opinion that protagon does not exist as a chemical
individual, but as a mixture of cerebrosides and phosphatides. It is
not easy to come to any decision on this disputed question. On the
one hand it must be recalled that several investigators call the impure
mixture of brain lipoids, protagon, which they obtain from the solution
in warm alcohol on cooking, and which is not purified, and this mixture
is claimed to be identical, without sufficient basis, with the substance
isolated and analyzed by Gamgee and Cramer. On the other hand
it cannot be denied that certain investigations, especially those of ROSEN-
HEIM and Tebb speak against the chemical individuality of protagon.
These investigations do not exclude the possibility that protagon is a
loose chemical combination between cerebroside and phosphatide, which
like other readily dissociable combinations, exist only under certain
conditions or in certain solvents. It is difficult to understand how a
mixture of amorphous or only difficultly crystallizable bodies can be
so easily crystallized and yield a product, which with proper care, can be
recrystallized repeatedly without changing its composition, and physical
properties. According to Rosenheim and Tebb if the proper quantity
is used in solution, a crystalline product can be obtained from the decom-
position products cf protagon, which has the same specific rotation as
protagon and can be repeatedly recrystallized without changing its
composition or its optical activity.2
A further study of these con-
ditions would naturally be of great interest.
As we are not decided whether protagon is only a mixture or is a body
contaminated with other substances, it is difficult to decide as to how
far the so-called decomposition products exist as preformed constituents
of the mixture or whether they are true decomposition products. On
boiling with baryta-water protagon yields cerebrosides (see below) and
the decomposition products of lecithin, namely, fatty acids, glycerophos-
phoric acid, and choline. Kossel and Freytag found three cerebro-
sides, namely, cerebrin, kerasix (homocerebrin), and encephalix.
According to Koch 3
the protagon molecule contains cerebroside, lecithin
and sulphuric acid (in ester-like combination with the cerebroside)
besides excess of cerebroside. Of interest is the finding of Kitagawa
and Thierfelder 4
that protagon dissolved in methyl alcohol contain-
ing chloroform, deposits crusts of cerebron (not pure) after a time at
1
Lesem, 1. c; Thudichum, 1. c; Worner and Thierfelder, Zeitschr. f. physiol.
Chem., 30.
1
Journ. of Physiol., 3"; Proc. physiol. Soc, January, 1908, p. 3.
* Zeitschr. f. physiol. Chem., 53.
* Kitagawa and Thierfelder, ibid., 49; Rosenheim and Tebb, Journ. of Physiol. 37
341 and 348.
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