 | |
| From A. M. Paterson, Cunningham’s Text-book of Anatomy. | |
| Fig. 2.—Deep Lymphatic Glands and Vessels of the Thorax andAbdomen (diagrammatic). Afferent vessels are represented by continuouslines and efferent and interglandular vessels by dotted lines. | |
C. Common iliac glands. C.I. Common intestinal trunk. D.C. Deep cervical glands. E.I. External iliac glands. I. Intercostal glands and vessels. I.I. Internal iliac glands. L. Lateral aortic glands. | M. Mediastinal glands and vessels. P.A. Pre-aortic glands and vessels. R.C. Receptaculum chylii. R.L.D. Right lymphatic duct. S. Sacral glands. S.A. Scalenus anticus muscle. T.D. Thoracic duct. |
The thoracic duct begins as an irregular dilatation known as the receptaculum chyli, opposite the first and second lumbar vertebrae, which receives all the abdominal lymphatics as well as those of the lower intercostal spaces. The duct runs up on the right of the aorta through the posterior mediastinum and then traverses the superior mediastinum to the left of the oesophagus. At the root of the neck it receives the lymphatics of the left arm and left side of the neck and opens into the beginning of the left innominate vein, usually by more than one opening.
The right lymphatic duct collects the lymphatics from the right side of the neck and thorax, the right arm, right lung, right side of the heart and upper surface of the liver; it is often represented by several ducts which open separately into the right innominate vein.
Haemolymph glands are structures which have only been noticed since 1884. They differ from lymphatic glands in their much greater vascularity. They assist the spleen in the destruction of red blood corpuscles, and probably explain or help to explain the fact that the spleen can be removed without ill effects. In man they extend along the vertebral column from the coeliac axis to the pelvis, but are specially numerous close to the renal arteries.
T. Lewis suggests that lymphatic and haemolymph glands should be classified in the following way:—
| Haemolymph Glands. | Haemal glands. | Simple. |
| Specialized (Spleen) | ||
| Haemal lymphatic glands. | 1. Blood and lymph sinuses separate. | |
| 2. Blood lymph sinuses. | ||
| 3. Other combined forms. | ||
| Lymphatic glands. |
Details and references will be found in papers by T. Lewis, J. Anat. & Phys. vol. xxxviii. p. 312; W. B. Drummond, Journ. Anat. and Phys. vol. xxxiv. p. 198; A. S. Warthin, Journ. Med. Research, 1901, p. 3, and H. Dayton, Am. Journ. of Med. Sciences, 1904, p. 448. For further details of man’s lymphatic system see The Lymphatics by Delamere, Poirier and Cuneo, translated by C. H. Leaf (London, 1903).
Embryology.—The lymphatic vessels are possibly developed by the hollowing out of mesenchyme cells in the same way that the arteries are; these cells subsequently coalesce and form tubes (see [Vascular System]). There is, however, a good deal of evidence to show that they are originally offshoots of the venous system, and that their permanent openings into the veins are either their primary points of communication or are secondarily acquired. The lymphatic and haemolymph glands are probably formed by the proliferation of lymphocytes around networks of lymphatic vessels; the dividing lymphocytes form the lymphoid tissue, and eventually the network breaks up to form distinct glands into which blood vessels penetrate. If the blood vessels enlarge more than the lymphatic, haemolymph glands result, but if the lymphatic vessels become predominant ordinary lymphatic glands are formed. At an early stage in the embryo pig two thoracic ducts are formed, one on either side of the aorta, and the incomplete fusion of these may account for the division often found in man’s duct. In the embryo pig too there have been found two pairs of lymph hearts for a short period.
See A. S. Warthin, Journ. Med. Research, vol. vii. p. 435; F. R. Sabin, Am. Journ. of Anat. i., 1902; and, for literature, Development of the Human Body, by J. P. McMurrich (London, 1906), and Quain’s Anatomy (vol. i., London, 1908).
Comparative Anatomy.—A lymphatic system is recognized in all the Craniata, and in the lower forms (fishes and Amphibia) it consists chiefly of lymph spaces and sinuses in communication with the coelom. In fishes, for instance, there is a large subvertebral lymph sinus surrounding the aorta and another within the spinal canal. In Amphibia the subvertebral sinus is also found, and in the Anura (frogs and toads) there is a great subcutaneous lymph sinus. Lymph hearts are muscular dilatations of vessels and are found in fishes, amphibians, reptiles and bird embryos, and drive the lymph into the veins; they are not known in adult mammals.