FIGURES 184 AND 185 



184 Transverse seetion lluoiiiili upper ])arl ol' left thoracic region in a 

 15.5 mm. cat embryo, (series 141, slide X, section IS), X 200. 



185 Same, section 21. 



1 Sympathetic nerve. 



8 Oesophagus. 



!) Trachea. 



16 Dorso-medial somatic venous tributaries. 



18 Peritracheal venous plexus. 



22 Vagus. 



23 Left carotid artery. 



33 Left subclavian arterJ^ 



38 Confluence of broncho-mediastinal duel .and prcazygos segment of 



thoracic duct. 

 40 Innominate vein. 



