4 THE CIRCULATION OF THE BLOOD

The heart described.-Its auricles and ventricles, and their action.-Valves of the heart.-Course of the blood through the heart.-The time the heart rests.-Times of its beating.-Its power and capacity.-Heart illustrated.-The arteries: their number and capacity.-Their position.-Their wounds; how known, how treated.-Their origin, and number.-Connection between arteries, and why.-Pulmonary arteries.-Capillaries: their rise, number, and use.-Their position.-Venous system.-Structure of the veins.-Their origin, and course.-Vein-valves, and their use.-Three classes of veins.-Forces of circulation in veins.-Pulmonary veins.-Portal system.-Blood: its color, and quantity in the body.-Time of its circuit through the body, and amount passing through the heart per hour.-What will promote a good circulation.-Clothing, proper food, etc.-Disturbing causes in the circulation

151. What are the organs used for the circulation of the blood?HBH 61.1

The Heart, the Arteries, the Capillaries, and the Veins.HBH 61.2

152. What is the central point of the circulation?HBH 61.3

The heart is the grand central engine of the human body, which propels the blood to all parts of the system. It is situated in the chest, resting by its lower surface on the diaphragm, and somewhat to the left of the middle line of the body. It is suspended to the spinal column in the upper part of the chest by the blood vessels and ligaments connected with its upper portion. It extends downward, forward, and slightly to the left, behind the breast-bone. The place where it is felt beating being against its extreme left and lower point.HBH 61.4

153. What is the heart?HBH 61.5

The human heart is a strong, hollow, heart-shaped organ, composed of muscular fibers, disposed in several layers, so as to form fibrous rings and bands, which afford it the greatest possible amount of strength for its bulk. It has several compartments and valves. The fibers of which the heart is composed cross themselves in at least three directions, and many of these fibers join with each other in many places. The heart is lined with a continuation of the lining of the veins, and covered with a similar coat. It is encased in an enclosing membrane called pericardium. This contains a small quantity of a fluid like water, so that the heart actually floats in a liquid, and does not rest firmly upon any hard surface.HBH 61.6

154. Is the heart a single or double organ?HBH 62.1

The heart is a double organ; externally it appears to be a single organ, but internally it is double. It is externally about five inches in length, by three and a half in diameter, and weighs about ten ounces. Internally, it contains four compartments; two right, and two left. These compartments are called Auricles and Ventricles. These pairs of Auricles and Ventricles have not any communication with each other, therefore they are considered as two distinct hearts. The right is called the venous and the left the arterial side of the heart. The whole heart will hold nearly a pint.HBH 62.2

155. What can you say of the auricles of the heart?HBH 62.3

The right auricle is larger than the left; its interior has five openings, and two valves. The auricles are very similar. They are the upper-most cavities of the heart, and are smaller than the ventricles, or lower ones. The auricles have thinner walls than the ventricles, but their walls are thicker than those of the veins. They are capable of considerable dilation, so that the receptacle of the blood may be enlarged in case of a sudden effort of the body when the blood is sent in great quantities to the heart. Were it otherwise the veins would be in danger of rupture. These auricles are constructed of a continuation of the veins that terminate in them. They are the inner extremities of the veins. Their name is derived from an appendage or extension; that in the right auricle appears a little like a dog’s ear.HBH 62.4

156. What of the ventricles of the heart?HBH 63.1

The ventricles are the lower cavities of the heart. Their walls being thicker than those of the auricles, they have more power of contraction, which is necessary, as they drive the blood from the heart. The right ventricle propels the blood only to the lungs, while the left ventricle sends it to all parts of the body except the lungs. The ventricles are similar, the right being a little more capacious, and its walls thinner, than the left. The inner surface of the ventricles is smooth, at the same time it is uneven, many bundles of fibers extending across the cavity, which gives them a spongy appearance.HBH 63.2

157. What further arrangement is connected with the auricles and ventricles of the heart?HBH 63.3

The auricles have several openings on their sides toward the veins, at which there are no valves, and one opening toward the ventricles, with valves, through which, in case of the right auricle, blood can flow back if much force is exerted; but in case of the left auricle none can flow backward, or the lungs might be endangered. There are only two openings to each ventricle, one into, and the other out of it; these are both situated at the upper part of the ventricle, and are both furnished with valves.HBH 63.4

158. What are these valves?HBH 64.1

The valves are muscular fibers arranged in such a form that the blood can pass through them; but the contracting of the ventricle presses the blood back against the valve and closes it so that the blood cannot pass back again. The same contraction of the muscles of the ventricle forces the valves open out into the arteries, and the pressure of the blood in the artery closes the valve again. Thus the ventricles by their alternate contraction and expansion, act very much on the principle of a force pump; sucking the blood into the heart from the veins and forcing it out again through the arteries.HBH 64.2

159. What is the course of the blood into and out of the heart?HBH 64.3

The venous or impure blood is received into the right auricle, and then passes into the right ventricle, which contracts and forces the blood into the lungs, where it is purified, and passes back into the left auricle. From the left auricle it passes into the left ventricle, which contracts and throws the blood through the arteries into all parts of the system except the lungs. This blood imparts nourishment to the bones, cartilages, ligaments, tendons, membranes, muscles, and nerves, and supplies the various secretory organs with the blood from which they separate their lubricating, solvent, and other fluids; and having served its purpose it returns again to the heart to be forced into the lungs, purified and again forced out into the system as above described.HBH 64.4

160. What then appears to be the necessity of two sets of auricles and ventricles, or two hearts?HBH 65.1

The necessity for two hearts arises from the fact that all the blood, as soon as it has made its circuit through the body, needs to be acted upon by the air, and must therefore be forced through the lungs; but the delicate structure of the lungs would not tolerate the force necessary to drive the blood through them and then out again into all parts of the body, or, if they would, such a force would drive the blood through them too rapidly; therefore, after the blood has been passed through the lungs, it is received by another heart, whose contraction throws the blood into all parts of the body.HBH 65.2

161. What causes the alternate contraction and dilation of the heart?HBH 65.3

It is the direct action of the nerves of organic life connected with the heart. When the blood passes into the right auricle of the heart, the nerves of the heart are immediately stimulated to action; force is communicated to the muscles, which contract, closing the upper valve of the auricle, forcing open the valve into the ventricle, where the presence of blood excites through the nerves the muscles of the ventricles, which contract, closing the valves into the auricles, and throwing the blood out of the heart. This is the constant action of each auricle and ventricle.HBH 65.4

162. Is the action of the heart continual?HBH 65.5

It is. The blood is the life of man, so it must be kept constantly flowing. If the heart should cease its work the blood would cease to circulate and we should immediately faint, or die. Both auricles of the heart contract at the same time, and this is closely followed by the contracting of the ventricles, which occasions the double beating which may be observed by listening carefully with the ear over the heart. It is similar to the beat and return in the ticking of a clock.HBH 65.6

163. If the heart is continually in action when does it get any rest?HBH 66.1

The contraction of the auricles occupies only one-fourth the whole time of a beat, so that the auricle rests the other three-fourths of the time. The contraction of the ventricle occupies one-half the time of the whole beat, so it rests the other half of the beat.HBH 66.2

164. How many times does the heart contract or beat in a minute?HBH 66.3

In health, at maturity, the heart beats from sixty to eighty times; more frequently in woman than in man. Early in life it beats oftener. In advanced years less frequently. The health, state of mind, and amount of exercise taken, also affect the pulse.HBH 66.4

165. How much power is exercised by the human heart in its pulsations?HBH 66.5

It is supposed that the left ventricle of the heart acts with a force equal to sixty pounds at every beat; or, at eighty beats per minute, the muscles of the human heart exert a force in one hour equal to two hundred and eighty-eight thousand pounds.HBH 66.6

166. How much blood passes through the heart in an hour?HBH 66.7

The capacity of each ventricle is between one and two ounces. At eighty beats per minute, if only one ounce is received and thrown out at eachHBH 66.8

PICTURE AND TEXT

beat, it will equal five pounds per minute, or more than a barrel per hour.HBH 67.1

Figure IX
PICTURE
THE HEART

167. What does Fig. IX represent?HBH 67.2

Fig. IX is an external view of the heart. a, left ventricle; b, right ventricle; c, e, f, aorta, or the principal artery leading from the left ventricle. It is through this that the blood passes to all parts of the system; g, h, i, are the internal and external arteries of the face, head, neck, arms, etc.; k, pulmonary artery; l, l, its right and left branches, which carry the impure or venous blood from the right ventricle into the capillary vessels of the lungs; m, m, veins of the lungs which carry the blood back from the lungs to the left auricle of the heart; n, right auricle; o, ascending vena cava-the great vein which returns the impure blood from the lower portion of the body to the right auricle of the heart; q, descending vena cava, or the great vein which returns the impure blood from the head and upper portion of the body to the right auricle. These unite to form the vena cava, or returning hollow; r, left auricle; s, left coronary artery, which carries the blood from the aorta into the substance of the heart; p, portal veins, which return the blood from the liver.HBH 67.3