254 MANUAL OF PHYSIOLOGY. 



7. The pulmonary arteries (P. A.) press steadily upon the 

 blood and force it through the following, viz. : 



8. Small pulmonary arterioles (P. a.), which regulate the flow 



into the capillaries. 



FIG. 113. 



Interior of Eight Auricle and Ventricle exposed by the removal of a part 

 of their walls. (Allen Thomson.) 1. Superior vena cava. 2. Inll-i -ior vena 

 cava. 2'. Hepatic veins. 3, 3', 3 /x . IIUUM- wall <>f right auricle. 4, 4. 

 Cavity of right ventricle. 4'. Papillary muscle. 5, 5', 5 X/ . Flaps of tri- 

 cuspid valve. 6. Pulmonary :irti>ry, in tin- wall of which a window has 

 been cut. 7. Placed on aorta is near the-ductus arteriosus. 



9. The pulmonary capillaries (P. C.), where the blood is ex- 

 posed to the air, and undergoes active gas-interchange. 



10. The pulmonary veins (P. V.), carrying the blood to the 

 left heart, and thus completing the circuit. 



