The lymphatics of the lungs are of large size, and are divided, as in other parts of the body, into a superficial and deep-seated set. The latter accompany the ramifications of the bloodvessels and air-tubes throughout the texture of the organ, and communicate at various points with the superficial vessels. The principal branches escape from the lung at its root, where they are joined by the superficial vessels, and pass with them through the large bronchial glands. The superficial lymphatics of the lung are larger than those of any other viscus ; they are situated in the interlobular fissures immediately under the pleura, and are injected with greater facility than the lymphatics of other parts of the body; their principal branches pass from the surface of the lung towards the inner edge and root of the organ, where they unite with the deep-seated ves sels, and pass with them through the bron chial glands. The vasa efferentia of these glands having communicated with the glands in the posterior mediastinum pass upwards on the trachea, where they meet with other glands with which they interchange branches; having entered the cervical region with the trachea, they unite freely with other lymphatics, espe cially with those of the thyroid gland, and ultimately terminate, on the left side, in the thoracic duct ; on the right, in the right lym phatic trunk, or separately in the large veins.
The lymphatics of the heart are neither large nor numerous; they proceed both from the sub stance and from the surface of the organ ac companying the principal bloodvessels; their appropriate glands are chiefly situated on the ascending thoracic aorta and trunk of the pul monary artery; where these vessels are covered by the pericardium, they ascend in front of the arch of the aorta, pass between the sternum and transverse veins, communicate freely with the large vessels of the anterior mediastinurn, and terminate with them on either side in the trunks of the system, the greater number, however, passing on the left sides to the tho racic duct.
The deep-seated lymphatics of the upper ex tremity successively accompany the digital arte ries, the superficial and deep palmar arches, the radial, ulnar, and interosseous arteries. At least two lymphatic vessels accompany each ar tery ; they communicate by short transverse branches with each other, and also at different points with the superficial lymphatics. At the bend of the elbows they unite into three or four vessels which pass up the arm with the bra chial artery to gain the axillary glands, into which they empty themselves. The small glands which not unfrequently may be found accompanying the brachial artery, and even, but more rarely, the ulnar or radial vessels do not generally intercept the deep lymphatic vessels, but the latter rather receive the efferent vessels from these glands, they having collected their afferent vessels from the surrounding tex tures.
The superficial lymphatics of the upper ex tremity in their passage to the axillary glands follow more or less the course of the subcuta neous veins. Those which accompany the ce phalic and basilic veins commence on the dorsal surface of the fingers, where they com municate with the digital lymphatics ; from thence they proceed over the metacarpus to the posterior surface of the forear m, tending with their accompanying veins towards its ulnar and ra dial edges, over which, sooner or later, they pass to gain the anterior surface, and at the bend of the elbow they have all collected in the neighbourhood of the internal condyle. The lymphatics accompanying thq median vein take origin from the palmarAurEice of the fingers, where they communicate with the digital lymphatics ; they take their course up wards first on the palm of the hand, then on the anterior surface of the forearm, and at the bend of the elbow join those already traced to the same point. The great majority of these vessels now continue their course upwards over the internal condyle to the inner side of the arm, some of them traversing the little gland or glands situated just above the internal condyle ; from thence they take the nearest route to gain the axillary glands, of which they form the principal vasa inferentia. Some three or four of the lymphatics, which in the forearia were associated with the branches of the ce-. phalic vein as far as the bend of the elbow, separate themselves from the rest, and ascend with this accompanying vein on the outer side of the biceps, and in the interval between the deltoid and pectoralis major muscles, where they meet with a gland which they traverse and ultimately pass with the vein over the pectorali3 minor muscle to gain the deep-seated lympha tics accompanying the axillary artery.
The axillary glands collect their vasa infe rentia also from the upper half of the anterior, posterior, and lateral surfaces of the trunk. From the anterior surface those on the ab domen above the umbilicus ascend; those on the upper part of the chest, joined by some from the cervical region, descend; those on a level with the axilla from the pectoral muscles and the glands of the breast take a transverse direction—all in short converging towards the axilla, where the glands in which they termi nate are situated. From the posterior surface of the trunk in a similar way they concentrate from the lumbar, cervical, and dorsal regions to pass over the posterior border of the axilla to reach the same glands.