FIGURES 172 AND 173 



172 Transverse section of left side of upper thoracic region of a 15 mm. 

 cat embryo, (series 143, slide XI, section 1C), X 200. 



173 Same, section 14. 



1 Sympathetic nerve. 



8 Oesophagus. 



9 Trachea. 



17 Prevertebral venous plexus. 



33 Left subclavian artery. 



35 Thoracic duct, preazygos segment. 



37 Broncho-mediastinal duct. 



38 Confluence of broncho-mediastinal duct and preazygos segment of 



thoracic duct. 

 40 Innominate vein. 



