One big artery, called the aorta, springs from the left ventricle; it runs back to the pelvis after giving off very many branches on its way and then divides into an artery for each leg. Its big branches divide into smaller and these into smaller again, until they become too small to be traced by the unaided eye. They spread through the whole body, to muscles, and bones, and skin, and brain, and stomach, and intestines, and liver, and kidneys; they finally end in the systemic capillaries. The systemic veins collect the blood from the capillaries of the different organs, and all these veins unite to form the superior and inferior vena cavœ or the upper and lower hollow veins. These carry the blood to the right auricle; thence it enters the right ventricle from which arises one vessel, the pulmonary artery; this divides into a branch for each lung ; each branch splits up into minute arteries in its own. lung, and these end in the pulmonary capillaries. From the pulmonary capillaries the blood of each lung is collected into two pulmonary veins, and the four pulmonary veins open into the left auricle.

What artery arises from the left ventricle ? To what point does It run? What does it give off on its course? How does it end? What becomes of its branches? In what do they end? What vessels collect the blood from the systemic capillaries?

Summary

One artery, the aorta, arises from the left ventricle. The blood carried out by the aorta comes back by the upper and lower venae cavœ to the right auricle; this blood then goes to the right ventricle and is sent thence through the pulmonary artery, which splits up into branches for the lungs. The blood, carried out by the pulmonary artery from the right ventricle of the heart, returns to the left auricle by four pulmonary veins, two from each lung; and then enters the left ventricle and begins its flow again through the aorta.