LYMPHATICS OF ALIMENTARY TRACT 733 



inferior gluteal (sciatic) and pudic, the middle hsemorrhoidal, and the lateral 

 sacral arteries. All the nodes are beneath the pelvic fascia, and are connected by 

 numerous anastomoses. They receive lymphatics from the structures supplied 

 by the corresponding arteries, namely, from the pelvic viscera, the perineum, and 

 the posterior surface of the thigh and gluteal region. Their efferent vessels pass 

 partly to the middle group of the common iliac nodes, and partly to the posterior 

 nodes of the same chain. 



The sacral nodes [Igl. sacrales]. — These nodes, 5 or 6 in number, lie in the 

 hollow of the sacrum, in or near the mid-hne. They receive afferent vessels 

 from rectum and prostate, and their efferents pass to the hypogastric and lumbar 

 nodes. 



2. THE LYMPHATIC VESSELS OF THE ABDOMINAL WALLS 



The lymphatic vessels of the abdominal walls are arranged in two sets, one of 

 which is subcutaneous and the other deep or aponeurotic. The subcutaneous 

 vessels form a rich network through all the subcutaneous tissue of the abdomen, 

 anastomosing above with the subcutaneous plexus of the thorax. The collecting 

 vessels converge toward the inguinal region, those from the posterior wall 

 curving forward along the crest of the ilium, and they all terminate in the super- 

 ficial inguinal nodes. 



The deep vessels drain along three principal lines. (1) A set of collecting 

 vessels follows the line of the deep epigastric artery to terminate in the lower 

 external iliac nodes; (2) a second set follows the deep circumflex iliac vessels to 

 the same nodes; and (3) a third set follows the lumbar vessels to terminate in the 

 nodes of the lumbar chain. A group of small epigastric nodes, which may be 

 regarded as offsets from the iliac chain, occur on the lymph-vessels which ac- 

 company the deep epigastric vessels, not far from their termination, and a 

 second less constant group of usually three small umbilical nodes occurs in the 

 vicinity of the umbilicus in the network covering the posterior layer of the 

 sheath of the rectus abdominis muscle. 



3. THE VISCERAL LYMPHATIC VESSELS OF THE ABDOMEN AND 



PELVIS 



The lymphatics to the viscera follow along the course of the arteries. At the 

 point where the artery of an organ branches from the aorta there is a group of 

 nodes which represents the main regional group, and a second chain of nodes 

 extends along the artery. The final arrangement of nodes and ducts varies with 

 each organ. 



Though the lymphatics follow the blood-vessels, the lymphatic capillaries in the regions where 

 their relations are known are separated from the vascular capillaries; in the intestinal vihi, 

 for example, the lymphatic capillaries are central, while the vascular capillary plexuses are 

 peripheral. The relation of the lymphatic capillaries to the essential structures of each organ, 

 that is to say, the arrangement of the lymphatics in the absorbing area, is not yet clear in many 

 organs, and this is a point which can be worked out by tracing the development and gradual 

 invasion of each organ by the lymphatics. The old theory of the origin of the lymphatics 

 from the tissue-spaces made this problem most difficult of attack. 



In almost all organs there is a peripheral or capsular lymphatic plexus, which 

 anastomoses with the parietal lymphatics, these anastomoses being particularly 

 well developed in the case of the liver. In addition there are one or two deep 

 plexuses in the great majority of the organs which drain partly directly to their 

 regional nodes and partly by way of the peripheral plexus. 



The Lymphatics of the Alimentary Tract 



The lymphatics of the mouth, pharynx, and oesophagus have already been 

 described (pp. 715, 730). In general, throughout the abdominal part of the ali- 

 mentary canal, the distribution of nodes is as follows: — (1) There are primary 

 regional nodes situated at the roots of the arteries as they leave the aorta, that is 

 to say, around the coeliac and the superior and inferior mesenteric arteries; these 



( 



