FIGURES 30 AND 31 



30 Transverse section through left side of lower cervical region in a 14 nun. cat 

 embryo (series 210, slide VIII, section 39) , X 225. 



31 Same, section 40. 



1 Sympathetic nerve. 



11 Jugular lymph sac. 



12 Jugular lymph sac, thoracic duct approach. 



16 Dorso-medial somatic venous tributaries. 



17 Prevertebral venous plexus. 



18 Peritracheal venous plexus. 



19 Suprathymic venous plexus. 



20 Subthymic venous plexus. 



21 Thymus. 



22 Vagus. 



23 Left carotid artery. 



24 Thyrocervical artery. 



25 Internal jugular vein. 



