FIGURE 100 



100 Transverse section of upper thoracic rcfjion in a 12 mm. cat embryo (series 

 78f slide IX, section 5), X 50. 



1 Sympathetic nerve. 



3 Right azygos vein, thoracic port ion. 



6 Precardinal or precava, resp. azygos of left side. 



7 Aorta. 



8 Oesophagus. 



9 Trachea. 



10 Pulmonary arterj'. 



16 Dorso-medial somatic venous tributaries. 



22 Vagus. 



31 Primitive ulnar veno-l3-mj)liatic. 



33 Subclavian artery. 



48 Right auricle. 



49 Left auricle. 



50 Right ventricle 



