802 THE VASCULAR SYSTEMS 



subscapular group. Those over the pectoral region, including the vessels from 

 the skin covering the peripheral part of the mamma, run backward, and those 

 over the Serratus magnus upward, to the pectoral group. Others near the lateral 

 margin of the sternum pass inward between the rib cartilages and end in the 

 internal mammary nodes, while the vessels of opposite sides anastomose across 

 the front of the sternum. A few vessels from the upper part of the pectoral 

 region pass upward over the clavicle to the supraclavicular group of cervical nodes. 



The lymphatic vessels of the mammary gland (Fig. 562) originate in a plexus 

 in the interlobular spaces and on the walls of the galactiferous ducts. Those from 

 the central part of the gland pass to an intricate plexus beneath the areola (sub- 

 areolar plexus), a plexus which also receives the lymphatics from the skin over 

 the central part of the gland. Its efferents are collected into two trunks which 

 pass to the pectoral group of axillary nodes. The vessels which drain the inner 

 (mesal) part of the gland pierce the thoracic wall and end in the internal mammary 

 nodes, while a vessel may occasionally emerge from the upper part of the gland 

 and piercing the Pectoralis major, to terminate in the subclavicular nodes 

 (Fig. 562). 



The deep lymphatics of the thoracic wall consist of: 



1. The lymphatics of the muscles which lie on the ribs; most of these terminate 

 in the axillary nodes, but some from the Pectoralis major pass to the internal 

 mammary nodes. 



2. The intercostal lymphatic vessels which drain the Intercostal muscles and 

 parietal pleura. Those draining the External intercostal muscles run backward 

 and, after receiving the vessels which accompany the posterior branches of the 

 intercostal arteries, terminate in the posterior intercostal nodes. Those of the 

 Internal intercostal muscles and parietal pleura consist of a single trunk in each 

 space. These trunks run forward in the subpleural tissue and the upper six 

 open separately into the internal mammary nodes or into the vessels which unite 

 them; those of the lower spaces unite to form a single trunk which terminates in 

 the lowest of the internal mammary nodes. 



3. The lymphatic vessels of the Diaphragm, which form two plexuses, one on 

 its thoracic and another on its abdominal surface. These plexuses anasto- 

 mose freely with each other, and are best marked on the parts covered respectively 

 by the pleurse and peritoneum. That - on the thoracic surface communicates 

 with the lymphatics of the costal and mediastinal parts of the pleura, and its 

 efferents consist of three groups: (a) anterior, passing to the nodes which lie 

 near the junction of the seventh rib with its cartilage; (6) middle, to the nodes on 

 the oesophagus and to those around the termination of the inferior vena cava; 

 and (c) posterior, to the nodes which surround the aorta at the point where this 

 vessel leaves the thoracic cavity. 



The plexus on the abdominal surface is composed of fine vessels, and anasto- 

 moses with the lymphatics of the liver and, at the periphery of the Diaphragm, 

 with those of the subperitoneal tissue. The efferents from the right half of this 

 plexus terminate partly in a group of nodes on the trunk of the corresponding 

 inferior phrenic artery, while others end in the right lateral aortic nodes. Those 

 from the left half of the plexus pass to the preaortic and lateral aortic nodes, 

 'and to the nodes on the terminal portion of the oesophagus. 



Applied Anatomy. The fact emphasized by Robinson that the peritoneum is a great 

 lymph sac explains the quick absorption of septic material and the rapid spread of infectious pro- 

 cesses. If the exudate clots and blocks the lymph channels, absorption is slow and life may be 

 saved. If it does not clot, absorption is rapid and death is certain. Whether it clots or not 

 depends on the nature of the bacteria present. Fowler, impressed by the fact that absorption 

 takes place most rapidly from the diaphragmatic region and least rapidly from the pelvic region, 

 advises placing the victim of peritonitis in bed, with his head and body elevated. 



