FIGURES 172 AND 173 



172 Transverse section o! left side of upper thoracic region of a 1') nun. 

 cat embryo, (series 143, slide XI, section 16), X 200. 



173 Same, section 14. 



1 Sympathetic nerve. 



8 Oesophagus. 



Trach(>a. 



17 Prevertebral venous ])lexus. 



33 Left subcla\ian artery. 



35 Thoracic duct, prcazygos segment. 



37 Broncho-mculiastinal duct. 



38 Confluence V)f broncho-n)ctlia.stinal duct and preazygos segment of 



thoracic duct. 

 4t) Innominate \cin. 



