FIGURES 206 AND 207 



206 Transverse section through middh> tlioraoic region in a 13.5 mm. cat 

 omhryo, (series 76, slide XT, section la) X 300. 



207 Same, section Ki. 



3 Riglit azygos \'ein, thoracic jjortion. 



4 Atroj^hying enibrj'onal vein, forming kernel in interior of develop- 



ing and replacing lymphatic space. 



5 Extraintimal or perivenous 1\ lupti.ii ic space surrounding degener- 



ating cmhi'Nonal \'ein 



7 Aorta. 



8 Oesophagus. 



15 Tiitci;iz\gos venous ])lexus. 



