FIGURES 2(14 AND 26o 



264 Same, section 8. 



265 Transverse section of middle thorafic rcsiion in a 10 mm. cat pm})rvo, 

 (series 253, slide XXIV. section (0 X 225. 



1 S^'iiipatlictic iicr\-('. 



3 Right azygos vein, thoracic jwrtion. 



4 Atrophying embryonal vein, forming kernel in inlericjr of developing 



and replacing lym])hatic space. 



5 Extraint ini;d oi' jjcrivciKius lym])hatic sjjace surrounding degen- 



erating embryonal vein. 



6 Left azygos vein, thoracic poriion. 



7 Aoi'ta. 



8 Oesophagus. 



15 Interazj'gos venous plexus. 

 34 Ventro-medial azygos plexus. 

 36 Thoracic duct, azygos segment. 



