218 HENRY K. DAVIS 



Croup II 



The thoracic ducts of this group (cases 1-6, figs. 10-15) begin 

 in the abdominal cavity as two ducts which extend cephalad 

 through the thorax. The right duct lies to the right of the 

 aorta and the left duct to the left of the aorta. The right duct 

 crosses in the thorax at the level of the 4th thoracic vertebra 

 dorsal to the aorta to join the left duct forming a single trunk 

 which empties into the venous system on the left side at the base 

 of the neck. The two ducts are connected by cross anastomosing 

 channels. This type of duct occurred in 6 cases out of 22, or 

 in 27.27 per cent. This form of duct corresponds to the thoracic 

 duct represented in Type 2. In proportion to the completeness 

 of the persistence of embryonic conditions these ducts have been 

 divided into three divisions, A, B and C. Lower ('80) and 

 Nuhn ('49) describe a similar thoracic duct. 



Division A. The thoracic duct of this division (fig. 10) 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 at the level of the lower third of 

 the body of the 2nd thoracic vertebra joins the left duct forming 

 a single trunk which continues cephalad to open into the left 

 subclavian vein a short distance from its junction with the in- 

 ternal jugular vein. The right duct lies to the right of the 

 aorta and is situated between the aorta and the vena azygos 

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

 are of equal calibre and are connected by numerous cross anas- 

 tomoses. Three of these are especially well developed (1) a 

 cephalic one which connects the cephalic end of the right duct 

 with the left; (2) one which is situated opposite the body of the 

 9th thoracic vertebra nearly transverse in direction; (3) and 

 one starting in the abdominal cavity on the right side and passing 

 cephalad and to the left to join the left duct opposite the body 

 of the 11th thoracic vertebra. There is no cisterna chyli. It is 

 represented in this case by a plexus of lymphatic vessels. This 

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



