The Lymphatic System is the means by which the liquid portion of the blood which exudes into the intercellular spaces is gathered up and returned to the blood, passing through the lymphatic glands on its way. The lymph capillaries gather up the fluid from the spaces, and enter a definite system of vessels, which carry the lymph to the groups of glands. Vessels leave these glands, and the lymph is carried to its final destination in the big veins at the root of the neck by one of the two terminal lymph vessels.

The Thoracic Duct is the larger of the two terminal vessels. It commences in the Receptaculum chyli (really a dilation of the vessel) which lies beneath the right crus of the diaphragm. The duct passes through the aortic opening in the diaphragm, and passes up on the right of the vertebral column. At the level of the fifth thoracic vertebra it crosses over to the left side, and passes up to enter the left innominate vein. The Receptaculum chyli receives the lymph from the lower extremities and the whole of the abdomen. The thoracic duct receives lymph from the left half of the thorax, the left upper extremity, and the left side of the head and neck.

The Right Lymphatic Duct is a very short vessel, not always present, about an inch long, which enters the right innominate vein. It receives lymph from the right half of the thorax, right upper extremity, and the right side of the head and neck.

The Lymphatic Glands and their vessels are arranged in two sets - superficial and deep - and are usually to be found on the course of the big veins and large spaces where there is connective tissue. The two sets anastomose with one another freely.

Head and Neck.

Occipital Glands, upon the upper part of trapezius or com-plexus, drain the occipital region of the scalp and upper and back part of the neck.

Mastoid Glands, on the upper part of sterno-mastoid and the mastoid bone, drain the parietal region of the scalp and the ear.

Facial Glands, small glands in different parts of the face, including several small groups situated beneath and behind the masseter muscle, draining the different parts of the face.

Superficial Cervical Glands lie superficial to the sterno-mastoid along the course of the external jugular veins. They drain the superficial part of the neck and mastoid region. There are also numerous small groups draining the tongue, front of the neck, pharynx, and larynx (see Fig. 59).

Deep Cervical Glands are in two groups, one beneath the sterno-mastoid lying along the course of the internal jugular vein. The other, embedded among the cords of the brachial plexus, is termed the supraclavicular group. These glands receive tributaries from the surrounding tissues and the groups of glands above them.

Upper Extremity.

Antecubital Glands, two or three small glands in front of the elbow, which drain the anterior surface of the forearm They are not always present.

Axillary Glands

These are arranged in four groups-(1) along the axillary vessels, (2) along the upper part of the axillary and the subclavian vessels, (3) between pectoralis major and serratus magnus, (4) along the subscapular vessels on the posterior wall of the axilla. They drain the upper limb and adjacent parts.

The Superficial Lymphatic Vessels of the upper limb begin by fine plexuses on the fronts of the fingers and palms of the hand. These converge to form vessels running along the sides of the fingers and back of the hand, and finally larger vessels are formed which follow the course of the veins and receive tributaries from the surrounding tissues, passing up to join the antecubital and axillary glands. The Deep Lymphatic Vessels commence in the deeper tissue, and follow the course of the deep vein to the glands.

Lower Extremity.

Anterior Tibial Gland, on the front of the upper part of-the interosseous membrane, drains the front of the leg.

Popliteal Glands, several glands in the popliteal space lying along the course of the vessels. These receive the tributaries from the anterior tibial gland and from the calf of the leg and foot.

Femoral Glands are in two sets-superficial and deep. They are all in Scarpa's triangle, arranged along the course of the vessels and along Poupart's ligament. They drain the whole of the lower limb.

The Lymphatic Vessels of the lower extremity are arranged in a very similar manner to those of the upper.

Trunk.

There are a large number of groups of glands in the abdomen and thorax which lie along the course of the vessels and in connection with the organs, and enter mainly the thoracic duct as described above. The lateral walls of the trunk are drained by the axillary and femoral groups of glands. The anterior walls are drained by some of the visceral groups, and the back is drained by groups of glands lying along the front of the vertebral column.