968 HUMAN ANATOMY. 



those below the left one. The third subgroup is formed by the pulmonary nodes, 

 usually of small size and situated in the hilus of the lungs, between the larger 

 divisions of the bronchi. 



The afferents of the bronchial nodes are (i) from the lungs, (2) from the lower 

 part of the trachea and from the bronchi, (3) from the heart, and (4) from the 

 posterior mediastinal nodes. Their efferents may either pass as a number of stems 

 to the thoracic duct or directly to the subclavian vein on the right side, but more 

 frequently they unite to form a single stem, with which the stems coming from the 

 sternal and anterior mediastinal nodes unite to form a single broncho-mediastinal 

 trunk (truncus bronchomediastinalis), which passes upward toward the confluence 

 of the internal jugular and subclavian veins. It either opens independently into the 

 subclavian vein, which is the most usual arrangement, or else, on the right side, it 

 unites with the subclavian and jugular trunks to form the right lymphatic duct or, on 

 the left side, it unites with the subclavian trunk to open into the arch of the thoracic 

 duct, into which it may also open directly. 



The Lymphatic Vessels. 



The cutaneous lymphatics of the thorax form a rich net-work extending 

 throughout the subcutaneous tissue and being continuous above with the subcutaneous 

 net-work of the cervical region and below with that of the abdomen. From the 

 net-work of the anterior surface a considerable number of stems arise, which pass 

 outward, the upper ones almost horizontally and the lower ones obliquely upward 

 and outward, to terminate in the anterior pectoral nodes of the axillary plexus 

 (Fig. 814). These stems form the principal path of the anterior thoracic drainage, 

 but, in addition, some stems which arise from the upper portion of the net-work 

 pass upward over the clavicle and terminate in some of the lower inferior deep 

 cervical nodes, and from the portions of the net-work near the median line short 

 stems perforate the intercostal spaces and terminate in the sternal nodes. Further- 

 more, it is to be noted that the net-works of either side are continuous across the 

 median line over the surface of the sternum, and there may consequently be a certain 

 amount of crossing in the lymph flow, that coming from the more median portions 

 of the net-work of the right half of the anterior thoracic wall, for instance, 

 terminating in the feft axillary nodes. These decussating paths are, however, of 

 comparatively little importance except in cases of stoppage of the normal flow to 

 the axillary nodes of the same side, and in such cases a collateral drainage may 

 also be established for the lower portion of the thoracic walls through the abdominal 

 lymphatics to the inguinal nodes. 



Upon the lateral portions of the thorax the net-work gives rise to some half 

 dozen stems which pass upwards to terminate in the inferior pectoral nodes of the 

 axillary plexus, and from the net-work of the posterior thoracic wall about ten or 

 twelve main stems arise which converge laterally to terminate in the subscapular 

 group of the axillary plexus. As was the case in the anterior net-work, so in the 

 posterior net-work some stems from the upper portions of the dorsal net-work pass to 

 the lower inferior deep cervical nodes, and below more or less anastomosis occurs 

 between the net-works of the thoracic and abdominal (lumbar) regions. 



The Mammary Gland. — The lymphatics of the mammary gland arise in the 

 deeper portions of the mammary tissue from sack-like enlargements situated in 

 the connecfive tissue between the various lobules of the gland. The majority of 

 the stems follow in general the course of the ducts and, passing toward the surface, 

 communicate with an exceedingly fine subareolar net-work, which is a special 

 development of the general subcutaneous net-work of the anterior thoracic wall. 

 F"rom the subareolar net-work two or more stems arise and form the principal paths 

 for the mammary lymph, but accessory paths are also furnished by stems which arise 

 from the sack-like enlargements and pass toward the periphery of the gland, 

 avoiding the subareolar net-work. 



The stems which arise from the subareolar net-work pass at first almost directly 

 outwards until they reach the lower border of the pectoralis major. They then 

 ascend along the lower edge of this muscle for a short distance, and eventually bend 



