64 



DEVELOPMENT OF THE SYSTEMIC LYMPHATIC VESSELS 



occupies sections 10 to 23 of slide vii in this embryo, and is 

 shown in the dorsal view of the reconstruction, fig. 89, to which 

 the individual sections following are referred for orientation. 



The process arises in the usual situation from the dorso-medial 

 aspect of the left jugular lymph sac and trends dorso-mesad 



across the internal jugular vein (series 189, slide vii, section 10, 

 fig. 43). In reference to the level of the common jugular conflu- 

 ence, which occurs in slide vii, section 26, the thoracic duct 

 approach in series 189 arises more anteriorly from the jugular 

 lymph sac than in the preceding series 210. Its extent and course 



