FIGURES 184 AND 185 



184 Transverse section through upper part of left thoracic region in a 

 15.5 mm. cat embryo, (series 141, slide X, section 18), X 200. 



185 Same, section 21. 



1 Sympathetic nerve. 



8 Oesophagus. 



9 Trachea. 



16 Dorso-medial somatic venous tributaries. 



18 Peritracheal venous plexus. 



22 Vagus. 



23 Left carotid artery. 



33 Left subclavian artery. 



38 Confluence of broncho-mediastinal duct and preazygos segment of 



thoracic duct. 

 40 Innominate vein. 



