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CADAVERIC   CHANGES   IN   THE   MUSCLES                                  127

in the pelvis. Post-mortem staining does not occur in the heart, but it may
contain the so-called " cardiac polypi " which are post-mortem fibrinous clots.

Hypostasis in internal organs, such as the brain, lungs, stomach? kidneys
and intestines, has to be distinguished from congestion or inflammation of
those organs.

Difference between Post-mortem Staining and Congestion in an Organ,—

Post-rnortem staining in an organ is irregular, and occurs on a dependent
part; redness caused by congestion is generally uniform and all over the
organ. The mucous membrane in post-mortem staining is dull and lustre-
less, but not so in congestion.

In post-mortem staining inflammatory exudation will not be seen, and
areas of redness alternating with pale areas will be found if a hollow viscus
is stretched out and held in front of light.


After death the muscular tissues of the body pass through three stages :
(1) Primary relaxation or flaccidity, (2) Cadaveric rigidity or rigor mortis,
(3) Secondary relaxation.

(1)  Primary   Relaxation   or   Flaccidity*—Soorx after   death   the   whole
muscular system commences to relax except in those cases where the muscles
have been in a contracted condition before death ; hence we notice that the
lower jaw of a dead body falls, the eyelids lose their tension, the extremities
become soft and flabby, and the joints are flexible.    But the _rnuscles are
contractile, and react to*external stimuli, mechanical or electrical, owing to
their retaining molecular life after somatic death.

This stage lasts from three to six hours, but the average is two or three
hours. One hour and fifty-one minutes is the average period of duration
in Bengal as found by Mackenzie.13

(2)  Cadaveric  Rigidity  or  Rigor Mortis.—This phenomenon, which is
also known as death stiffening, comes on immediately after the muscles have
lost the power of contractility, and affects all the muscles of the body, both
voluntary and involuntary.

A satisfactory theory has not yet been advanced to explain the chemical
changes which occur in the muscle tissues during the process of rigor mortis,
but Szent-Gyorgyi and others 14 have shown from their recent investigations
that adenosine triphosphate (ATP) plays a fundamental role not only in
the normal contraction and relaxation of living muscles, but in determining
the physical condition of the muscle proteins. According to them the muscle
protein which was formerly known as myosin consists of a combination of
two proteins, viz. myosin and actin. The combined form, is called actomyosin,
and possesses the property of contractility and relaxation in the presence of
adenosine triphosphate which is normally closely bound to the muscle

They have further proved that the presence of adenosine triphospliate
absorbed in the muscle proteins is essential for the preservation of the normal
degree of hydration, which is concerned in maintaining the suppleness of
living muscle. After death, the adenosine triphosphate is decomposed pro-
gressively and disappears from the muscles, and thus causes dehydration
which results in rigor mortis.

During rigor mortis the reaction of the muscle changes from slightly
alkaline to distinctly acid, due probably to the formation of lactic acid
during the process of the breaking down of the muscle proteins.

13.    Jnd. Med. Gaz., June 1889, p. 167.

14.   Sydney Smith and F. S. Fiddles, Forens. Med., Ed. IX, p. 21.