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586 MUSCLES.
shaken with ether to remove the fat. The residue is dissolved in water
and phosphoric acid is added, and the solution repeatedly shaken with fresh
quantities of ether, which dissolves the lactic acid. The ether is new
distilled from the united ethereal extracts, the residue dissolved in water,
and this solution carefully warmed on the water-bath to remove the last
traces of ether and volatile acids. A solution of zinc lactate is prepared
from this filtered solution by boiling with zinc carbonate, and this is
evaporated until crystallization commences, and is then allowed to stand
over sulphuric acid. An analysis of the salts is necessary in careful
work. In regard to methods for the detection and quantitative estima-
tion of lactic acid we must refer to larger hand-books.
Fat is never absent in the muscles. Some fat is always found in the
intermuscular connective tissue; but the muscle-fibers themselves also
contain fat. The quantity of fat in the real muscle substance is always
small, usually amounting to about 10 p. m. or somewhat more. A con-
siderable quantity of fat in the muscle-fibers is found only in fatty degenera-
tion. A part of the muscle-fat can be readily extracted, while another
part can be extracted only with the greatest difficulty. This latter
part, it is claimed, exists finely divided in the contractile substance
itself and is richer in free fatty acids, standing, according to Zuntz and
Bogdanow,1
in close relation to the activity of the muscles because
it is consumed during work. Lecithin is a regular constituent of the
muscles, and it is quite possible that the fat which is difficult of extrac-
tion and which is rich in fatty acids depends in part on a decomposition
of the lecithin and the phosphatides. Erlandsen has shown that
phosphatides of various kinds occur in the muscles, the quantities
varying in different muscles. According to him the ox-heart muscle
is richer in phosphatides than the muscle of the thigh, and Rubow 2
claims that the heart of the dog is richer in phosphatides than the striated
muscle. Erlandsen found lecithin and diamino-phosphatide in the
heart as well as the thigh-muscle, while the monoamido-phosphatide
cuorin, which occurs abundantly in the heart, is found as traces in the
thigh-muscle. Costantino 3
has carried on investigations on the divi-
sion of the inorganic and organic phosphorus in striated and smooth
muscles.
The Mineral Bodies of the Muscles. The ash remaining after burning
the muscle, which amounts to about 10-15 p. m., calculated on the moist
muscle, is acid in reaction. The largest constituent of the ash is potas-
sium, whose occurrence, according to Macallum,4
is restricted to the dark
1
Arch. f. ( Anat. u.) Physiol., 1897.
2
Erlandsen, Zeitschr. f. physiol. Chem., 51; Rubow, Arch. f. exp. Path. u. Pharm.,
52.
1
Bioch. Zeitschr., 43.
Journ. of Physiol., 32.
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