pulled out to a point, and closed at a little distance from the divided
inner coats. If a large artery is torn asunder in the dead body, this
stretching out and contraction of the sheath will prevent injection
passing; in short, the immediate effects of the injury are such as to
favour the instant formation of coagula, by which the hemorrhage is
arrested until the orifices of the vessel be permanently closed by the
adhesive process. Thus, in instances where the whole of an extremity
has been torn off, the patients have generally lost but a very small
quantity of blood.
From wounds of veins the blood flows, not in a sub-saltatory but in a
uniform stream: its colour is dark, and the flow is easily suppressed.
The common opinion is, that to place a ligature on a vein is dangerous,
and to be scrupulously avoided. The process of reparation, besides,
in a wounded vein, is different from that in an artery. Veins are
less disposed to the secreting action by which adhesion is perfected;
and, when inflamed, the inflammation is extremely apt to extend along
the coats of the vessel; which latter circumstance has been ascribed
to the great proportion of cellular tissue in their coats. When
punctured longitudinally, the lips of the wound remain in contact,
and cicatrisation, by means of effused lymph, is soon effected; in
fact, the wound heals by the first intention. But if opened obliquely
or transversely, not to a great extent, the immediate result is
discharge of blood, and, when this has ceased, a coagulum forms in
the wound, the margins of which remain separate; and this coagulum
generally communicates with blood effused into the sheath of the
vessel. After some time, the lips of the wound, encircling the coagulum
which occupies the aperture, and which has temporarily averted the
hemorrhage, become somewhat turgid, and increased in vascularity;
they then appear to assume a secreting action, by which a membranous
substance, of extreme delicacy, is produced; and the extent of this
membrane is increased until it form an expansion, investing the outer
surface of the clot; it then becomes thickened, by addition of matter,
similar to itself, from the recent vessels which ramify in it. At the
same time it forms adhesions to the surrounding cellular tissue, and
resembles the original tunics of the vein. After being consolidated,
so as to prevent the flow of blood through that part, the coagulum,
formed to arrest the hemorrhage until a more complete barrier should
be furnished, is gradually absorbed. But the membrane long remains
smooth, thin, and diaphanous, and can be thereby readily distinguished
from the original coats. This reparative process is much longer in
being finished than the corresponding one in arteries; and, from what
has been stated, it is evident that the two actions differ in other
respects than the time requisite to complete them. When a vein has been
completely divided, the extremities are closed by means similar to
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