56 



THE STUDY OF CHICK EMBRYOS 



Heart and Blood-vessels. — As seen in the dorsal view of the embryo, the 

 heart tube is bent to the right. Viewed from the ventral side, the bend is to the 

 left (right of embryo) (Fig. 40). After receiving the vitelline veins cephalad to 

 the fovea cardiaca the double- walled tube of the heart dilates and bends ventrad 



Optic vesicle 



Paired ventral aorta 



Ventral aorta 

 Bulbus cordis 



Ventricle - 



Splanchnic mesoderm 

 Fovea cardiaca 



R. descending aorta 



Vascular plexus 



Splanchnic mesoderm 



Notochord 

 Mes. segment 



Segmental zone 



Fore-brain 



Fhar. pouch I 

 Descending aorta 



Fhar. pouch II 

 Somatopleure 



Left vitelline vein 

 Entoderm 



Section medullary lube 



Somatopleure 



aorta 



Medullary tube 

 Splanchnic mesoderm 



Capillary plexus 



ssss — Somatopleure 

 Neural groove 



Fig: 40. — Ventral reconstruction of a thirty-six-hour chick embryo. The entoderm has been removed 

 save about and caudal to the fovea cardiaca. X 38. 



and to the right (left of Fig. 43). It then is flexed dorsad and to the median line, 

 and narrows to form the ventral aorta. The aorta lies ventrad to the pharynx 

 and divides at the boundary line between the mid- and hind-brain into two 

 ventral aorta. These diverge and course dorsad around the pharynx. Before 



