FIGURE 17 



17 Transverse section of upper thoracic region of 14 mm. embryo (series 37, 

 slide XIII, section 12), X 150. 



1 Sympathetic nerve. 



3 Precardinal or precava, resp. azygos of right side. 



6 Precardinal or precava, resp. a^ygos of left side. 



7 Aorta. 



8 Oesophagus. 

 Trachea. 



22 Vagus. 



53 Precaval lymphatics. 



