DEVELOPMENT LYMPHATIC SYSTEM IN AMNIOTES 



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Figures 1, 2, 3 



1, Precarciinal vein 



2, Duct of Cuvier 



3, Postcardinal vein 



4, External jugular-cephalic vein 



5, Subclavian vein 



6, Jugular lymphsac 



7, Thoracic duct approach of jugular 



lymphsac 



8, Common jugular lymphatico- ve- 



nous tap 



9, Jugulo-subclavian lymphatico-ve- 



nous tap 



10, Thoracic duct anlages 



11, Thoracic duct 



In a succeeding (15 mm.) stage (fig. 2) a number of the proximal 

 mesenchymal tissue spaces have united with each other and have 

 joined the thoracic duct approach of the jugular lymph sac (11). 

 In the same way longer channel segments have formed further 

 caudad by fusion of a number of the distal anlages (10). Injec- 

 tion, of the jugular sac in this stage, would show, in comparison 

 with figure 1, a caudal extension of the thoracic duct (11) beyond 

 the postcardinal junction. As revealed by the injection alone 

 the extension might be interpreted, as has been done, as a cen- 

 trifugal growth or sprout caudad from the jugular Ijinph sac 



