FIGURES 122 AND 123 



122 Same, section 11. 



123 Transverse section through ventral part of upper thoracic region in a 14 mm. 

 cat embryo (series 214, slide XIII, section 4) X 225. 



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. 



7 Aorta. 



9 Trachea. 



10 Pulmonary artery. 



18 Peritracheal venous plexus. 



22 Vagus. 



32 Ventral mediastinal venous plexus. 



