FIGURES 262 AND 263 



262 Same, section 33. 



263 Transverse section of middle thoracic region in a 14 mm. cat embryo, 

 (series 211, slide XII, section 2) X 225. 



1 Sympathetic nerve. 



2 Intersegmental arteries. 



3 Right azygos vein, thoracic portion. 



4 Atrophying embryonal vein, forming kernel in interior of developing 



and replacing lymphatic space. 



5 Extraintimal or perivenous lymphatic space surrounding degen- 



erating embryonal vein. 



6 Left azygos vein, thoracic portion. 



7 Aorta 



8 Oesophagus. 



15 Interazygos venous plexus. 

 34 Ventro-medial azygos plexus. 

 36 Thoracic duct, azygos segment. 



