FIGURES 146 AND 147 



146 Transverse section through ventral part of upper thoracic region in 

 a 15.5 mm. cat embryo (series 215, slide XIV, section 31), X 225. 



147 Transverse section through ventral portion of upper thoracic region in 

 a 16 mm. cat embryo (series 230, slide XII, section 25), X 225. 



3 Right precaval vein. 



4 Atrophying embryonal vein, forming kernel in interior of developing 



and replacing lymphatic space. 



5 Extraintimal or perivenous lymphatic space surrounding degenerat- 



ing embryonal vein. 



6 Precardinal or precava of left side. 



7 Aorta. 



8 Oesophagus. 



9 Trachea. 



10 Pulmonary artery. 



22 Vagus. 



32 Ventral mediastinal venous plexus. 



