234 HENRY K. DAVIS 



In their thoracic portion, they He at first within the posterior 

 mediastinum, but cephalad they enter the superior mediastinum. 

 In the posterior mediastinum, they he ventrad to the bodies of 

 the 11th to the 5th thoracic vertebrae, and have ventral to 

 them the pericardium, the oesophagus, and the arch of the 

 aorta. The thoracic aorta lies to the left and to the right are the 

 right pleura and the greater azygos vein. The caudal right 

 intercostal arteries pass between them and the bodies of the 

 vertebrae, as does also the terminal portion of the hemiazygos 

 vein. In the superior mediastinum, they rest upon the caudal 

 part of the longus colli muscle, being separated by it from the 

 bodies of the three cephalic thoracic vertebrae. Ventrad they 

 are in relation with the origin of the left subclavian artery and 

 with the vertebral vein; to the left is the pleura and to the right 

 are the oesophagus and the left recurrent laryngeal nerve. 



The arch of these is in relation caudad with the apex of the 

 left lung and with the left subclavian artery. Dorsad and to the 

 left is the vertebral vein and to the right and ventrad are the 

 left common carotid artery, the left internal jugular vein, and 

 the left vagus nerve. 



This type of duct belongs clearly to Type 6 of my classification. 

 It occurred in 14 cases out of 22, or in 63.63 per cent. This 

 type of duct is described as normal by all anatomists. 



Group VII 



The thoracic duct of this type begins in the abdominal cavity 

 as a single trunk and passes cephalad into the thorax lying on the 

 left side of the aorta. In the thorax it crosses over to the right 

 side and opens into the right angulus venosus. I was unable 

 to find any ducts of this type described in the literature, nor did 

 I find any among my own cases. It seems strange that ducts 

 of this type and also of Type 5 have not been reported, inasmuch 

 as ducts of all the other types have been found. 



