FIGURES 260 AND 261 



260 Same, section 9. 



261 Transverse section of lower thoracic region in a 16 mm. cat embryo, 

 (series 96, slide XII, section 32) X 200. 



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. 



36 Thoracic duct, azygos segment. 



