ances, a combination of these causes may be active.

Direct involvement of vessels is the commoner form of circulatory
disturbance which occasions lameness, and the most frequent cause is of
parasitic origin. Sclerostomiasis with attendant arteritis, thrombus
formation and subsequent lodgement of emboli in the iliac, femoral, or
other arteries, causes sufficient obstruction to prevent free
circulation of blood, and the characteristic lameness of thrombosis
results.

Indirect injury to vessels may occur because of contused wounds and
subsequent inflammation of tissues supplied by such vessels. If the
injury be of sufficient extent, considerable extravasation of blood will
take place and the painfully swollen parts necessarily impair
locomotion. In such instances lymph vessels participate in the
disturbance, and the condition then becomes one wherein lymphangitis is
the predominant disturbing element.

Angiomatous tumors are occasionally found affecting horses'
legs--usually the result of some injury; and because of their size or
position, they mechanically interfere with function. Furthermore, when
such tumors are located on the inner or flexor side of joints, enough
pain is occasioned that affected animals show evidence of distress,
usually by intermittent lameness.

Horses do not suffer from distension of veins as does man, that is,
there is rarely to be seen a case wherein much disturbance from this
source exists.

AFFECTIONS OF LYMPH VESSELS AND GLANDS.

Inflamed lymph vessels and glands, the result of various causes, is a
rather common source of lameness of horses. When one considers the
proportion of tissue that is composed of lymph vessels and glands, it is
then obvious that inflammation of these structures should cause a
painful affection of members, when so affected, and that marked lameness
and, in some instances, general constitutional disturbance such as
anorexia, hyperthermia and general circulatory disorder are to follow.

Lymphangitis is most frequently occasioned by the introduction of septic
material into the tissues; consequently, infectious lymphangitis is more
frequently observed than the non-infectious type.

Specific infectious forms of lymphangitis are seen in glanders and in
strangles; infectious types of this disturbance are found in many
instances where, initially, a localized or circumscribed infection has
occurred--the contagium having been introduced by way of an injury. An
exampl