222 HENRY K. DAVIS 



vertebra and crossing dorsal to the aorta reaches the left side 

 where it continues its course cephalad to open into the angulus 

 venosus formed by the junction of the left internal jugular and 

 left subclavian veins. The right duct lies to the right of the 

 aorta. It passes up into the thorax from the abdominal cavity 

 and ends at the lower level of the 7th thoracic vertebra. The 

 portion cephalad of this has atrophied. The two ducts are 

 joined together by numerous cross anastomoses. There is no 

 cisterna chyli present. It is represented by a plexus of lymphatic 

 vessels. 



In figures 13, 14 and 15, the right duct corresponds to the 

 right duct described in case 3 (fig. 12) with the exception that it 

 empties into the left subclavian vein instead of the angulus 

 venosus. The left ducts are essentially the same as in case 3 

 (fig. 12). In case 4 (fig. 13) there is no cisterna chyli but there 

 is a lymphatic plexus. In case 5 (fig. 14) there are two cysternae 

 chyli. The right duct is a direct continuation of the right cis- 

 terna chyli. The left cisterna chyli is connected to both the 

 right and left ducts. The left duct, however, is not a direct 

 continuation from the left cisterna chyli. In case 6 (fig. 15) 

 there is a single cisterna chyli. The right duct is a direct con- 

 tinuation of this cisterna. The left duct is also connected with 

 it. In this case there is a division of the right duct into two 

 branches. This bifurcation takes place at the lower level of the 

 body of the 6th thoracic vertebra and the two branches unite 

 again to form a single trunk at the upper level of the body of 

 the 5th thoracic vertebra. In these 4 cases the lymphatics on 

 the left side of the aorta including the left duct, drain in a caudal 

 direction. Lymph glands are associated with the thoracic duct 

 in cases 3, 4 and 5 (figs. 12-14). A further account of these will 

 be given in dealing with the variations. 



The arrangement of the two ducts in these 4 cases points 

 to an originally double thoracic duct, as in case 2 (fig. 11). There 

 is represented in these 4 cases another more advanced stage 

 in the atrophy of the left duct. In case 2 there was a reduction 

 in the size of the left duct, while in these 4 cases there is a reduction 

 in size and a complete atrophy of a portion of the left duct. This 

 type of duct occurred in 4 cases out of the 22, or in 18.18 per cent. 



