LYMPHATICS OF THE MAMMARY GLAND 723 



and nerves, the efferents from which nodes pass either into the lower deep cer- 

 vical lymph-nodes or directly into the subclavian trunk. 



The lymphatics of the shoulder-joint have recently been described by Tananesco. He 

 finds a ring of lymphatics in the joint capsule, whose efferents, in the main, following the arteries, 

 run to the central and subclavian groups of axillary nodes. 



C. THE LYMPHATICS OF THE THORAX 



The lymphatics of the thorax will be considered under the following divisions: 

 the superficial vessels, the deep nodes, and the deep vessels. 



1. THE SUPERFICIAL LYMPHATIC VESSELS OF THE THORAX 



The superficial lymphatics of the thorax pass almost exclusively to the axillary 

 nodes, and may be regarded as forming three sets, a ventral, a lateral, and a 

 dorsal. The ventral set drains the thoracic integument, which extends form 

 the median line and the clavicle over to the lateral border of the chest, and includes 

 the vessels of the mammary gland, which will, however, be described separately. 

 The majority of the vessels from this area end in the anterior pectoral group of 

 axillary nodes, a few, which arise beneath the clavicle, passing to the supra- 

 clavicular nodes, and a few perforating the intercostal spaces and ending in the 

 chain of nodes along the internal mammary artery. 



It has been shown that an injection into the subcutaneous plexus near the median Line 

 passes to the opposite side, and that, in addition to the anastomosis between the networks of 

 the two sides of the thorax which this result manifests, there may also be a few collecting trunks 

 crossing the median line, and, furthermore, anastomoses occur between the superficial networks 

 of the anterior thoracic and abdominal walls. Thus while the main channel of lymphatic 

 drainage is through the axilla, there are minor accessory channels to (1) the supraclavicular 

 nodes, (2) to the axilla of the opposite side, (3) to the internal mammary chain, and (4) in iso- 

 lated cases even to the inguinal nodes. These accessory channels may become more open in 

 cases of obstruction to the main channel. 



The lateral set of superficial thoracic lymphatics is much less extensive than 

 the anterior, and its collecting vessels pass upward to open into the posterior 

 pectoral group of axillary nodes. 



The dorsal set, which occupies the subcutaneous tissue of the dorsal thoracic 

 wall, sends its vessels to the subscapular group of axillary nodes. 



The Lymphatics of the Mammary Gland (Figs 566, 568) 



The lymphatic network over the peripheral portions of the mammary gland is 

 like that of the rest of the thoracic wall. In the areola, however, the capillaries 

 are far more abundant, forming a double subareolar plexus. The superficial 

 plexus is so dense that its meshes can be seen only with a lens. The deeper plexus 

 not only drains the superficial plexus, but receives the vessels from the mammary 

 gland itself, and from it arise two large trunks, one from the inferior and one from 

 the superior part of the plexus. These two vessels pass to one or two of the nodes 

 belonging to the anterior pectoral group of axillary nodes. In addition there may 

 be — (1) one or two vessels passing to the nodes along the axillary artery; (2) in 

 rare cases a vessel passing directly to the subclavian nodes. There is also a defi- 

 nite channel from the medial margin of the gland to the internal mammary nodes, 

 the ducts following the perforating branches of the internal mammary vessels, 

 and it may be noted that the crossed anastomosis and that with the abdominal 

 network, mentioned in connection with the superficial thoracic vessels, may, on 

 occasions, serve as channels for the mammary drainage. 



There is also clinical evidence indicating that lymphatic vessels from the 

 lower and medial aspect of the mammary gland may pass through the abdom- 

 inal wall in the angle between the xiphoid process and the costal cartilages, 

 establishing a communication with the lymphatics of the abdomen in the 

 diaphragmatic region. 



Lymphatics of the thoracic muscles. — The recent studies of Aagaard make it probable 

 that muscles are provided with lymphatics. Whether his findings wiU be substantiated or 

 not, however, it is unquestioned that lymphatic vessels course through the pectoral muscles — 

 some passing to the axillary, others to the subclavian, and still others to the internal mammary 

 chain of nodes. This would suffice to explain the fact that cancer of the breast may extend 

 into and through the pectoral muscles. 



