to tumours of
blood vessels. The view that varix is congenital in origin, as was first
suggested by Virchow, is supported by the fact that in a large
proportion of cases the condition is hereditary; not only may several
members of the same family in succeeding generations suffer from varix,
but it is often found that the same vein, or segment of a vein, is
involved in all of them. The frequent occurrence of varix in youth is
also an indication of its congenital origin.

In the majority of cases it is only when some exciting factor comes into
operation that the clinical phenomena associated with varix appear. The
most common exciting cause is increased pressure within the veins, and
this may be produced in a variety of ways. In certain diseases of the
heart, lungs, and liver, for example, the venous pressure may be so
raised as to cause a localised dilatation of such veins as are
congenitally weak. The direct pressure of a tumour, or of the gravid
uterus on the large venous trunks in the pelvis, may so obstruct the
flow as to distend the veins of the lower extremity. It is a common
experience in women that the signs of varix date from an antecedent
pregnancy. The importance of the wearing of tight garters as a factor in
the production of varicose veins has been exaggerated, although it must
be admitted that this practice is calculated to aggravate the condition
when it is once established. It has been proved experimentally that the
backward pressure in the veins may be greatly increased by straining, a
fact which helps to explain the frequency with which varicosity occurs
in the lower limbs of athletes and of those whose occupation involves
repeated and violent muscular efforts. There is reason to believe,
moreover, that a sudden strain may, by rupturing the valves and so
rendering them incompetent, induce varicosity independently of any
congenital defect. Prolonged standing or walking, by allowing gravity to
act on the column of blood in the veins of the lower limbs, is also an
important determining factor in the production of varix.

Thrombosis of the deep veins--in the leg, for example--may induce marked
dilatation of the superficial veins, by throwing an increased amount of
work upon them. This is to be looked upon rather as a compensatory
hypertrophy of the superficial vessels than as a true varix.

_Morbid Anatomy._--In the lower extremity the varicosity most commonly
affects the vessels of the great saphena syst