AFFECTIONS OF BLOOD VESSELS.
Lameness caused by disturbances of circulation may be due to structural affection of vessels, or functional disorders of the heart, and in some instances, 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 example of this kind is to be seen in a wound perforating the tibial fascia, where the injury is inflicted by means of a horse being kicked by another animal shod with sharp shoe-calks. Cases of this kind invariably result in a septic lymphangitis, and frequently lymphadenitis also occurs, for the inguinal lymph glands are so situated that their becoming contaminated is almost certain.