FIGURES 204 AND 205 



204 Transverse section through middle thoracic region of a 13.5 mm. cat- 

 embryo; (series 189, slide X, section 15) X 225. 



205 Same, section 16. 



1 Sympathetic nerve. 



3 Right azygos vein, thoracic portion. 



6 Left azygos ve.n, thoracic portion. 



7 Aorta. 



8 Oesophagus. 



34 Ventro-medial azygos plexus. 



