CHANGES IN CIRCULATION WITH HATCHING 



183 



bloods pass to both the right ventricle and the left auricle. When relaxation 

 of the ventricle occurs, the blood passes into both right and left ventricles. 

 From the left ventricle the blood is forced into the fourth aortic arch, which 

 joins the dorsal aorta. Branches supply the head region. The blood from 

 the right ventricle passes out through the sixth aortic arch and most of it 



RIGHT SIDE 



LEFT SIDE 



R. LUNG 



°2 <*J 



ALLANTOIS 



ALLANTdS 

 0, AND CO. 



C0 2 C0 2 AND 2 



EMBRYO EMBRYO 

 Fig. 110. The path of the blood through the heart of a chick embryo. Only 

 the main systemic circulation and the pulmonary circulation are shown. Circula- 

 tion to and from the head region is omitted. On the right side the main systemic 

 artery, 4, connects the left ventricle, L.V., with the dorsal aorta. As the systemic 

 artery curves posteriorly it receives the ductus arteriosus from the pulmonary 

 artery, 6. As long as the ductus arteriosus is open blood flows from the right 

 ventricle, R.V., into the dorsal aorta and does not to any appreciable extent flow 

 through the lungs. 



