The differential diagnosis is to be made from abscess, bursal cyst, enlarged glands, and sarcoma, especially pulsating sarcoma of one of the bones entering into the knee joint.

The choice of operation lies between ligation of the femoral artery in Hunter’s canal, and Matas’ operation of aneurysmo-arteriorrhaphy.  The success which attends the Hunterian operation is evidenced by the fact that Syme performed it thirty-seven times without a single failure.  If it fails, the old operation should be considered, but it is a more serious operation, and one which is more liable to be followed by gangrene of the limb.  Experience shows that ligation of the vein, or even the removal of a portion of it, is not necessarily followed by gangrene.  The risk of gangrene is diminished by a course of digital compression of the femoral artery, before operating on the aneurysm.

Aneurysmal varix is sometimes met with in the region of the popliteal space.  It is characterised by the usual symptoms, and is treated by palliative measures, or by ligation of the artery above and below the point of communication.

Aneurysm in the #leg and foot# is rare.  It is almost always traumatic, and is treated by excision of the sac.

CHAPTER XV

THE LYMPH VESSELS AND GLANDS

Anatomy and Physiology—­INJURIES OF LYMPH VESSELS—­Wounds of
    thoracic duct—­DISEASES OF LYMPH VESSELS—­Lymphangitis: 
    Varieties—­Lymphangiectasis—­Filarial
    disease—­Lymphangioma—­DISEASES OF LYMPH
    GLANDS—­Lymphadenitis:  Septic; Tuberculous;
    Syphilitic—­Lymphad
enoma—­Leucocythaemia—­TUMOURS.

#Surgical Anatomy and Physiology.#—­Lymph is essentially blood plasma, which has passed through the walls of capillaries.  After bathing and nourishing the tissues, it is collected by lymph vessels, which return it to the blood stream by way of the thoracic duct.  These lymph vessels take origin in the lymph spaces of the tissues and in the walls of serous cavities, and they usually run alongside blood vessels—­perivascular lymph vessels.  They have a structure similar to that of veins, but are more abundantly provided with valves.  Along the course of the lymph trunks are the lymph glands, which possess a definite capsule and are composed of a reticulated connective tissue, the spaces of which are packed with leucocytes.  The glands act as filters, arresting not only inert substances, such as blood pigment circulating in the lymph, but also living elements, such as cancer cells or bacteria.  As it passes through a gland the lymph is brought into intimate contact with the leucocytes, and in bacterial infections there is always a struggle between the organisms and the leucocytes, so that the glands may be looked upon as an important line of defence, retarding or preventing the passage of bacteria and their products into the general circulation.  The infective agent, moreover, in order to reach the blood stream, must usually overcome the resistance of several glands.