r28 



THE LYMPHATIC SYSTEM 



Most of the other variations — the frequent presence of longer or shorter doublings of the 

 duct with anastomoses between the two parts, the numerous variations in the region of the 

 receptaculum chjdi — are easily explained by the fact that the duct and receptaculum pass 

 through a stage in development in which they form richly anastomosing plexuses around the 

 aorta. 



The Right Terminal Collecting Ducts 



On the right side the jugular, subclavian, and broncho-mediastinal trunks 

 usually open separate^ into the subclavian vein, the orifices of the first two 

 being near together. When the jugular and subclavian trunks unite, the com- 

 mon duct is termed the right lymphatic duct; this is a rare form, and it is still 

 more rare for the three ducts to unite to form a common stem (fig. 572). These 

 variations have the same explanation, embryologically, as was given for the 

 corresponding variations on the left side. 



Fig. 572. — Terminal Collecting Ducts on the Right Side. (Poirier and Cuneo.) 



Node of deep cervical 

 chain 



Jugular trunk 



Subclavian trunk 



•\ Broncho-mediastina' 

 \ trunk 



Node of internal mam- 

 mary chain 



Right lymphatic duct 



Subclavian trunk 



Broncho-mediastinal 

 trunk 



Jugular trunk 



Right lymphatic duct 

 ~ Broncho-mediastinal trunk 



Node of internal mammary chain 



The Deep Lymphatic Vessels 



As with the nodes, the deep lymphatic vessels of the thorax may be divided 

 into a parietal and a visceral group. To the former group may be assigned the 

 lymphatics of the intercostal spaces and those of the diaphragm. 



The intercostal lymphatics form plexuses in each intercostal space, which 

 receive lymi)h from the periosteum of the ribs and from the parietal pleura, and 

 from which the drainage is either ventral or dorsal. From the dorsal half of 

 each space the drainage is to the intercostal nodes, Avhile from the ventral half it is 

 toward the internal niainiiiary nodes. 



The lymphatics of the diaphragm. — ^Therc is an exceedingly rich plexus of 

 capillaries Ijotli on the pleural and on the abdominal surface of the diaphragm, 

 especially in the region of the central tendon, these ph^xuses lying in the subserous 

 layers and being freely connected by vessels which perforate the muscle. There 

 is, however, only sligiit communication between the plexuses of the right and left 

 sides of the diaphragm. The vessels lie between the coarse muscle bundles, 

 forming a very characteristic picture, in which the lymphatics stream outward 

 radially, like the spokes of a wheel. The colle(;ting vessels empty into three 

 groups of small nodes on the convex surface. The ventral group lies ventral to 

 the central tendon. Two or three nodes in the centre of this group receive 



