I06 THE STUDY OF SIX AND TEN MILLIMETER PIG EMBRYOS 



\T\olome 



Ant. cardinal vein 



R. alriiim 



Somatoplcur, 



Olfactory pil 



—Descending aorta 



Pharynx 



Pericardial cavity 



Bulbus cordis 



7"i Inicephalon 



Fig. 108. — Transverse section through the bulbus cordis and olfactory pits of a 6 mm. pig embryo. 



X 26.5. 



A S/);hi;/ cord 



Mxotom 



Descending aorta 

 Esopfiat^u 



Sinus venosiis 

 Valve of sinus venosiis 



R. air ill ni' 

 Atrio-ventricular fora nun 



Interventricular siplnni 



I common cardinal vein 



[ nicrvcniriciilar foramen 



% — l\'ricardial cavity 



R. vcnlridc- 



Somaliipliiii i- 



Fig. 109. — Transverse section through the four chambers of the heart of a 6 mm. pig embryo. X 26.5. 



