236 HENRY K. DAVIS 



Group IX 



In case 22 (fig. 31) the thoracic duct begins at the upper level 

 of the 9th thoracic vertebra b;y^ the confluence of a plexus of 

 lymphatic vessels. It lies on the left side of the aorta and in 

 this position continues its direction cephalad and opposite the 

 body of the 1st thoracic vertebra begins to incline to the left and 

 then caudad dividing into two branches which open into the left 

 subclavian vein. The caudal branch terminates singly but the 

 cephalic branch divides into three branches just before its termi- 

 nation and opens into the left subclavian vein by three branches. 

 This duct in its abdominal portion receives the lumbar and 

 intestinal lymphatics, in its thoracic portion the collaterals 

 which drain the intercostal spaces and in its cervical portion the 

 left internal jugular and subclavian trunks. 



Cameron ('02) describes a similar case in which the thoracic 

 duct runs its entire course on the left side of the aorta. This 

 type of duct belongs clearly to Type 9 of my classification. It 

 occurred in 1 case out of 22 in my series, or in 4.545 per cent, 



VARIATIONS • 



In 11 cases out of 22, or in 50 per cent, there is a cisterna chyli 

 present (figs. 14-18, 20, 22, 24, 26, 28, 29). In one of these 

 cases (fig. 14) there is a double cisterna chyli. There is also a 

 double cisterna chyli in case 23 (fig. 32). This case differs from 

 the previous one in that a cisterna chyli is placed on each lumbar 

 trunk and the two lumbar trunks unite to form a single thoracic 

 duct. This case has not been considered among my series be- 

 cause nearly the entire thoracic portion of the duct had been 

 destroyed at the post mortem. Jossifow ('06) reports a similar 

 case in which there was a cisterna chyli on each of the lumbar 

 trunks. Instead of the caudal portion of the duct being dilated 

 as a cisterna chyli it may be represented by a plexus of lymph 

 channels. This condition was found in 10 cases out of the 22, 

 or in 45.45 per cent (figs. 10-13, 21, 23, 25, 27, 30, 31). In 1 

 case out of the 22, or in 4.545 per cent, the thoracic duct is formed 

 by the confluence of the right and left lumbar and intestinal 



