FIGURES ISti AND 187 



1,S6 Transverse section of left upper thoraeic rejiion in a 13..") mm. cat 

 embryo, (series 223, slide VIIT. section 8!)), X 225. 

 187 Same, section 4(J. 



1 Sympathetic nerve. 



4 Atrophying embryonal vein, forming kernel in interior of developing 



and rei)lacinfi lym])hatic space. 



5 Extraint imal or iici-ivenous lympliat ic sj)ac(> sui'roundinji; degenerat- 



ing embryonal \'cin. 



S Oesophagus, 



9 Trachea. 



22 Vagus. 



33 Left subclavian a it cry. 



40 Innominate vein. 



41 Vertebral artery. 



43 Costo-cer\ifal artery, 

 4.") Innomin.ali' arlcr\-. 



