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PROTEINS OF THE MUSCLES. 567
quickly at the temperature of the body. Muscle-plasma from mammals
coagulates slowly, according to vv. Furth, even at the temperature of
the room, though only slightly, and it can hardly be considered as a
process comparable with the coagulation of the blood. Indeed the ques-
tion may be asked whether a true muscle-plasma does exist in warm-
blooded animals, or whether the rluid obtained from such muscles
exactly represents the plasma of the living muscle. According to Kuhne
and v. Furth the reaction remains alkaline during coagulation, while
Halliburton, Stewart and Sollmann find that it becomes acid.
Earlier investigators held that the clot consists of a globulin called
myosin, while v. Furth claims that it consists of two coagulated pro-
teins, myosin-fibrin and myogen-fibrin.
The study of the proteins of the muscles, as well as their nomen-
clature, has changed markedly in the last few years, and it is questionable
whether an essential difference exists between the proteins of the muscle-
plasma and the muscle-serum of warm-blooded animals. Nevertheless
it is necessary to discuss separately the proteins of the dead muscle as
well as those of the muscle-plasma.
The proteins of the dead muscle are in part soluble in water or dilute
salt solutions, and in part are insoluble therein. Myosin and musculin
and also myoglobulin and myoalbumin, which exist to a very slight
extent and are perhaps only derived from the remaining lymph, belong
to the first group, and the stroma substances of the muscle-tubes belong
to the second group.
Myosin was first discovered by Kuhne, and constitutes the principal
mass of the soluble proteins of the dead muscle. It is generally considered
as the most essential coagulation product of muscle-plasma. The name
myosin, Kuhne also gives to the mother-substance of the plasma-clot,
and this mother-substance forms, according to certain investigators,
the principal mass of contractile protoplasm. The findings as to the oc-
currence cf myosin in other organs besides the muscles require further
confirmation. The quantity of myosin in the muscles of different animals
varies, according to Danilewsky,1
between 30 and 110 p. m.
Myosin, as obtained from dead muscles, is a globulin whose elementary
composition, according to Chittenden and Cummins.2
is, on an average,
the following: C 52.28, H 7.11, N 16.77, S 1.27, O 22.03 per cent. If
the myosin separates as fibers, or if a myosin solution with a minimum
quantity of alkali is allowed to evaporate to a gelatinous mass on a
microscope-slide, doubly refracting myosin may be obtained. Myosin
has the general properties of the globulins and is readily converted into
1
Zeitsohr. f. physiol. Chem., 7.
5
Studies from the Physiol. Chem. Laboratory of Yale College, New Haven, 3, 115.
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