CHAPTER I

The Heart

Valvular Affections-Causes of Heart Disease-Careful Exami nations Necessary-Treatment of Palpitation-Blood Analysis -Anæmia.

HEART DISEASE. The heart is a hollow muscle which withdraws blood from one set of blood vessels (the veins) and pumps it into another set (the arteries) and thus keeps the blood moving about the body. Within the heart are chambers and valves to prevent the blood from flowing back from the arteries into the heart and from the heart into the veins, as the valves in a pump prevent the water from flowing back into the well when the piston is lowered. In heart disease the muscle is either altered in structure through the influence of poisons-most of which are produced by the germs causing the acute diseases-or the valves of the heart become defective; that is, the valves do not close properly and are leaky, or else they become obstructed. Such defects constitute what is called valvular disease, which is the most common form of chronic disease of the heart. The effect of such a condition is that the heart does not pump sufficient blood into the arteries, because it leaks back into the [Text continued on page 441.]

Plate X

DIAGRAM OF THE CIRCULATION

The Left Auricle receives from the lungs the fresh, bright-red blood (indicated in Light Red) through the Pulmonary Veins. From the left auricle the blood passes into the Left Ventricle, and is then distributed through the Systemic Arteries to the liver, kidneys, intestines, and other parts of the body, at length reaching the Systemic Capillaries.

The Portal Veins carry the blood to the liver, where bile is formed and important changes effected in the blood.

Returning from the various organs and the body tissues, by way of the Hepatic, Intestinal, and other Capillaries, through the Systemic Veins, it carries with it the carbonic acid given off during the waste of tissue, and which imparts to it a dark tint.

This dark-red blood (Dark-Red Portions in Diagram) finally reaches the heart again through the Hepatic Veins which empty it into the Right Auricle. It then passes into the Right Ventricle, which pumps it through the Pulmonary Arteries into the lungs. Here it is purified by being exposed to the oxygen of the air, and in its new condition is returned through the Pulmonary Capillaries and Veins to the left auricle.