FIGURES 24i TO 247 



244 Transverse section of lower thoracic region of a 14 mm. cat embryo, 

 (series 34, slide XXI, section 18) X 225. 



245 Same, section 19. 



246 Same, section through middle thoracic region, slide XXVIII, section 17. 



247 Same, section 18. 



1 Sympathetic nerve. 



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. 



