My object is to erect, as it were, in this book, a little auricle, or spot of concentrated hearing, where the hearts of my readers may listen, and join in the song of their country's singing men and singing women.

A, superior vena cava; B, right auricle; C, right ventricle; D, left ventricle; E, left auricle; F, pulmonary vein; H, pulmonary artery; K, aorta; L, right subclavian artery; M, right common carotid artery; N, left common carotid artery.

The two largest veins in the body, the superior vena cava and the inferior vena cava, open into the right auricle.

These two veins bring venous blood from all parts of the body, and pour it into the right auricle, whence it passes into the right ventricle.

Four veins, called the pulmonary veins, open into the left auricle, two from each lung.

Thus the pulmonary artery carries venous blood from the right ventricle to the lungs, as the pulmonary veins carry arterial blood from the lungs to the left auricle.

They begin in the minute capillaries at the extremities of the four limbs, and everywhere throughout the body, and passing onwards toward the heart, receive constantly fresh accessions on the way from myriad other veins bringing blood from other wayside capillaries, till the central veins gradually unite into larger and larger vessels until at length they form the two great vessels which open into the right auricle of the heart.

These two large trunks meet as they enter the right auricle.

The four pulmonary veins, as we have learned, carry the arterial blood from the lungs to the left auricle.

We may conveniently begin with the portion of blood contained at any moment in the right auricle.

The superior and inferior venæ cavæ are busily filling the auricle with dark, impure blood.

The four pulmonary veins bring back bright, scarlet blood, and pour it into the left auricle of the heart, whence it passes through the mitral valve into the left ventricle.

[Illustration: Fig. 75.Diagram illustrating the Circulation. 1, right auricle; 2, left auricle; 3, right ventricle; 4, left ventricle; 5, vena cava superior; 6, vena cava inferior; 7, pulmonary arteries; 8, lungs; 9, pulmonary veins; 10, aorta; 11, alimentary canal; 12, liver; 13, hepatic artery; 14, portal vein; 15, hepatic vein.

The blood is returned to the right auricle (not to either of the venæ cavæ) by the coronary vein.

The heart muscle, endeavoring to compensate for the over-exertion, may become much thickened, making the ventricles smaller, and so fail to do its duty in properly pumping forward the blood which rushes in from the auricle.

A, left ventricle; B, right ventricle; C, left auricle; D, right auricle; E, superior vena cava; F, pulmonary artery; G, aorta; H, arch of the aorta; K, innominate artery; L, right common carotid artery; M, right subclavian artery; N, thyroid cartilage forming upper portion of the larynx; O, trachea.

A, left ventricle; B, right ventricle; C, left auricle; D, right auricle; E, superior vena cava; F, pulmonary artery; G, aorta; H, arch of the aorta; K, innominate artery; L, right common carotid artery; M, right subclavian artery; N, thyroid cartilage forming upper portion of the larynx; O, trachea.

oreja, f., auricle, ear.

Pinnæ sub-opposite, divergent, narrowly oblong, obtuse; base truncate, cordate or clasping, occasionally auricled; lower pinnæ often with orbicular or cordate pinnules.

Pinnæ opposite, oblong, entire or finely crenate, and auricled at the base.

Pinnæ scarcely an inch long, the lower ones very much shorter, alternate, spreading, finely serrate or incised, the base auricled.

[Illustration: Sori of Scolopendrium vulgare] (1) Scolopendrium vulgàre PHYLLÌTIS SCOLOPÉNDRIUM Fronds thick and leathery, oblong-lanceolate from an auricled, heart-shaped base, ten to twenty inches long and one to two inches wide.

Pinnæ linear-lanceolate, scythe-shaped, auricled on the upper side, and with bristly teeth; fertile pinnæ contracted toward the top, bearing two rows of sori, which soon become confluent and cover the entire surface.

Pinnæ broadly lanceolate-falcate or the lowest triangular, strongly auricled on the upper side, densely spinulose-toothed.

EUSTACHIO, BARTOLOMMEO, an Italian physician of the 16th century; settled at Rome, made several anatomical discoveries, among others those of the tube from the middle ear to the mouth, and a valve on the wall of the right auricle of the heart, both called Eustachian after him.