220 HENRY K. DAVIS 



Division B. The thoracic duct of this division (fig. 11) begins 

 in the abdominal cavity as two ducts which pass cephalad through 

 the thorax. The right duct at the upper level of the 5th thoracic 

 vertebra begins to incline to the left and passing dorsal to the 

 aorta reaches the left side and joins the left duct at the level of 

 the lower third of the body of the 2nd thoracic vertebra forming 

 a single trunk which passes cephalad. This trunk at the lower 

 level of the 7th cervical vertebra divides into three branches which 

 do not become united again before opening into the venous 

 system. The most cephalic branch opens into the left subclavian 

 vein a short distance distal to its junction with the left internal 

 jugular vein. The intermediate branch opens into the angulus 

 venosus formed by the junction of the left internal jugular and 

 left subclavian veins and the most caudal branch opens into the 

 left vertebral vein a short distance medial to its junction with 

 the left innominate vein. The right duct lies to the right of the 

 aorta and is placed between the aorta and the vena azygos major. 

 The left duct lies to the left of the aorta. The two ducts are of 

 unequal size, the right duct being of much greater caliber than 

 the left duct. The cross anastomosing channels in this case 

 are not as numerous as in case 1 (fig. 10) . The chief anastomosis 

 is the cephalic one which joins the cephalic end of the right duct 

 with the left duct. The reduction in caliber of the left duct 

 and the decrease in the numl)er of cross anastomoses point to a 

 stage in the atrophy of the left duct. There is no cisterna chyli 

 present. It is represented by a plexus of lymphatic vessels. 

 This type of duct occurred in 1 case out of 22, or in 4.545 per 

 cent (fig. 2). 



Division C. In cases 3 and 4 (figs. 12-13), in cases 5 and 

 G (figs. 14-15) there is a partial doubling of the caudal portion 

 of the thoracic duct. In each case the caudal portion of the right 

 duct is complete but the left duct has partially atrophied. 



In case 3 (fig. 12) the thoracic duct begins in the abdominal 

 cavity as two ducts which pass cephalad into the thorax. The 

 right duct lies to the right of the aorta and is placed between 

 the aorta and vena azygos major. It begins to incline to the 

 left opposite the inferior level of the body of the 4th thoracic 



