PLATE 13 



EXPLANATION OF FIGURE 



24 Drawn from a reconstruction of a chick embryo of 7 days (series no. 512) 

 Ventral view. 



1, aorta 



2, dorsal aortic roots 



3, aortic arch VI 



3n, pulmonary artery 

 5, celiac artery 

 7, carotid artery 



10, precardinal vein 



11, subclavian vein 



12, duct of Cuvier 



14, part of splanchnic plexus of veins 



15, jugular lymph sac 



15a, thoracic duct 'approach' of jugular 

 lymph sa:' 



16, groups of developing blood cells 

 16a, blood cells dorsal to aortic roots 



and arches 



17, thoracic duct, ventral plexus (homo- 

 logue of azygos segment) 



17a, thoracic duct (homologue of i)re- 

 azygos segment) 



18, lymphatics along aortic arches 



19, lymphatics dorsal to aortic roots 

 and arches 



21, mesenteric lymphatics 



188: 



