THORACIC DUCT, the name applied to the tubular structure in which the ab sorbent system of vessels may be said to terminate, and into which the lacteals of the intestine ultimately pour their con tained fluid. It thus receives (1) the products of digestion or chyle from the lacteal vessels of the intestine, and (2) the lymph or fluid, brought as the elab orated waste-matters of the body from the tissues by the absorbent system of vessels or lymphatics. Being poured into the thoracic duct, these products, which are destined to replenish the blood, and thus renovate the tissues, are in due course poured into the circulation. The thoracic duct of man exists as a tubular structure attaining a length of about 18 or 20 inches. It extends from the second lumbar vertebra to the root of the neck, where it ends in the angle formed by the junction of the left internal jugular and subclavian veins, into which vessels its contents are therefore poured. At its
commencement in the abdomen it ex hibits a dilatation, termed the recep taculum chyli, which receives the lym phatics of the lower extremities. The thoracic duct has a flexuous course, and exhibits an irregular or contracted ap pearance. It is provided internally with valves, preventing the backflow of its contained fluid. Occasionally it divides above into two branches; and a right thoracic duct is normally found as a short trunk attaining about an inch in length, and devoted to the reception of the lymph from the right side of the head and neck, from the right side of the chest and heart, and from other regions on that side of the body. In birds, the right thoracic duct may be equally devel oped with tie left.