PLATE 15 



EXPLANATION OF FIGURE 



26 Drawn from a reconstruction of a chick embryo of 8 days (series no. 513). 

 Ventral view. 



1, aorta 



2, dorsal aortic roots 



3, aortic arch VI 



3a, pulmonary artery 



4, aortic arch IV 



5, celiac artery 



6, notocord 



7, carotid artery 



9, superior mesenteric artery 



10, precardinal (jugular) vein 



11, subclavian vein 



12, duct of Cuvier 

 15, jugular lymph sac 



15a, thoracic duct 'approach' of jugular 

 lymph sac 



17, thoracic duct, ventral plexus (homo- 

 logue of azygos segment 



17a, thoracic duct (homologue of pre- 

 azygos segment) 



18, lymphatics along aortic arches and 

 duct of Cuvier 



19, lymphatics dorsal to aortic roots 

 and arches 



20, lymphatics dorso-Iateral to aorta 



21, mesenteric lymphatics 



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