LYMPHATIC GLANDS, small organs, round and smooth and comparatively solid, which form part of the lymphatic system in vertebrates. (See LACTEALS; LYMPH). Into these, sooner or later in their course, the other lymphatic vessels run, and from them emerge again. The lymphatic glands are highly im portant structures, since only after passing through them does the lymph contain, in any abundance, lymph-corpuscles. In size the glands may be compared to small almonds, and they are generally arranged in groups. Each gland is entered by a number of afferent vessels which bring lymph to it, while those (efferent vessels) which leave the gland carry lymph away from it. Externally a lymphatic gland presents an envelope of connective tissue, from which the stroma, consisting of a fibrous frame work of processes, is prolonged into the in terior of the gland. Within the stroma the essential gland-structure is contained. Within the stroma also, as well as within the softer portions or pulp contained in the meshes of the fibrous network, minute blood-vessels are distributed. are added to the lymph in the glands, while in the composition of its fluid it undergoes further elaboration. The lymphatic glands are regarded as factories of leucocytes or white blood cells. The lymphatic trunks of the greater part of the body finally pour their contents into the thoracic duct, a small tube which opens into the current of the blood at the point of junction of the internal jugular and subclavian veins of the left side of the body. On the right side of the body is a
still smaller duct which receives the contents of the lymphatics of the right half of the chest, the right arm and the right side of the head and neck; and this smaller lymphatic channel or right lymphatic duct opens into the angle formed by the junction of the right jugular and subclavian veins, similarly to its larger neighbor of the left side. The thoracic duct begins in the upper part of the abdomen and runs up in front of the spine to the root of the neck, where it opens into the great veins. The re. ceptaculum chyli, or cistern of the chyle, is the dilation at the commencement of the thoracic duct in the abdomen, which receives the con tents of the lacteals or intestinal lymphatics. The orifices by which the thoracic duct and right lymphatic duct open into their respective great veins are guarded by valves which permit the lymph to flow from the ducts into the veins, but prevent the flow of blood into the ducts.
The spleen has been considered by physiolo gists to he merely a ductless lymphatic gland of large size, since it appears to be concerned in the elaboration of the blood, and also to he a place of disintegration of the red corpuscles and a manufactory of the white corpuscles of the blood. And the thymus, another ductless gland, has also been supposed to he connected with the function of blood-elaboration, and thus to he associated with the lymphatic system.