DEVELOPMENT OF THE THORACIC DUCT 71 



sis of the reduplicated or multiple thoracic duct terminations oc- 

 casionally encountered in the adult as above described (cf.p. 66, 

 fig. 56, series 212, slide ix, figs. 34 to 42). 



In fig. 73 (series 92, slide ix, section 9) the subclavian approach 

 (14) is much reduced, and lies along the lateral aspect of the com- 

 mon jugular vein '(26). Its connection with the thoracic duct 

 approach (12) is plainly visible, passing between the main vein 

 (26) and the thyro-cervical artery (24). Dorsal somatic and 

 prevertebral venous tributaries (16), approaching the dorso- 

 medial angle of the common jugular vein (26), intersect the course 

 of the thoracic duct approach, and begin to divide the same into 

 a medial and a lateral element. This division is completed in 

 the following section (fig. 74) in which the united dorsal and pre- 

 vertebral tributaries form a venous trunk of considerable size 

 (16) which is approaching its confluence with the common jugular 

 vein by passing between the lateral and medial components of 

 the thoracic duct approach. In other words, the appearance of 

 the thoracic duct approach in this and in the following sections 

 is the expression of the ventro-mesal arched course of this structure 

 across the fork or angle between the common jugular vein (26) and 

 the terminal of its ventro-medial tributary plexus (16). The recon- 

 structions shown in figs. 89, 90 and 91 indicate this topographical 

 relationship clearly. The blind mesal end of the arched process 

 (12) now lies mesal to the tributary vein (16) and dorsal to the 

 sympathetic nerve (1). In the following section (section 11 of 

 slide ix, fig. 75), the dorso-medial venous tributary (16) is elong- 

 ated and close to the main vessel, while the reduced sections of 

 the thoracic duct approach lie on either sid of the same, as indi- 

 cated by the forked leader (12). The subclavian approach (14), 

 still prominent and connected with the medial section of the 

 thoracic duct approach in the preceding section 10 (fig. 74), 

 appears now in section 1 1 reduced to a detached small blind end 

 (not labelled in the figure), close to the lateral wall of the main 

 vein and ventral to the thyro-cervical arterj^ (24)- In the suc- 

 ceeding section 12 (fig. 76) the dorso-medial venous tributary 

 (superior intercostal vein) enters the common jugular trunk. 

 The lateral portion of the thoracic duct approach (not labelled 



