PULSE (Lot. pulses, a beating, from pcllcre, to drive). The rhythmical expansion of the arter ies due to the blood-waves caused by successive contractions of the heart. The arteries are elas tic tubes and there is injected into them at each contraction of the heart ventricles from two to four ounces of blood. As a consequence, an al ready full hut contracted artery becomes dis tended, lengthened, and uplifted, giving rise to the sensation in the examining finger which is called the pulse. The pulse-wave due to any given beat of the heart is not perceptible at the same moment in all the arteries of the body. The difference in time is proportioned to the distance of the arteries from the heart, and rarely amounts to more than IA or of a second. The pulse is usually felt at the radial or thumb side of the wrist, the artery being near the surface at this point and easily compressed against the bone. It may, however, be perceived in many other situations, notably at the point where the facial artery crosses the lower jaw, in the tem poral artery above the ear, the carotid in the neck, the brachial in the arm, and the femoral just below the fold of the thigh.
The pulse rate varies greatly in health accord ing to age, sex, temperament, exercise or rest, emotional states, temperature, time of day, pos ture, atmospheric pressure, mid personal idiosyn crasy. Before birth the average number of pul sations per minute is 150; in the newly born, from 140 to 130; during the first year of life, 130 to 115; during the second year, 115 to 100; about the seventh year, 90 to 85; about the 14th year, 85 to 80; in adult life, SO to 70; in old age, 70 to GO; in decrepitude, 75 to 65. In the female and in persons of a sanguine temperament the pulse rate is more rapid by several beats in the minute than in males and individuals of a phlegmatic type. The rate is also higher after a meal and during exercise. The pulse is most frequent in the morning and becomes gradually slower as the day advances; it is more rapid in the standing than in the sitting or recumbent posture; high temperatures also accelerate it. During sleep the pulse is usually slower than in the waking state. Forty is not an uncommon rate, and instances have been known in which the pulsations were only 30 or more rarely 20 to the minute.
In disease the pulse presents wide variations in rate, regularity, volume, and tension, and is a taluable guide in diagnosis and in estimating the physical condition of the patient, and disturb ances of its relation to respiration and tempera ture are always significant. Excessive slowness of the pulse (brayeardia) occurs in some dis eases of the heart, in conditions of collapse, in meningitis, in cerebral tumors, and in jaundice. It is also observed in convalescence from acute fevers and is probably an expression of exhaus tion. As a physiological phenomenon brady cardia occurs in the puerperal state, and in hun ger. As a general rule in disease the pulse is
more apt to be abnormally fast (tachycardia) than slow. Nearly every disturbance of health tends to quicken the pulse; rapid heart action is the constant accompaniment of acute inflam mation, of fever in all forms, and of most heart diseases. When the intervals between successive beats of the heart are not of uniform length, the pulse is said to be irregular. A pulse inter mits when a beat is dropped out of every four or more pulsations. Another form of irregularity is known as the pulsus bigeminus or allarythmia. In this the beats occur in successive pairs with an abnormally long interval between them. Pvl sus paradoxes consists in the diminution or total disappearance of the pulse during inspiration, and is a very rare occurrence.
The pulse is said to be full when the volume of the pulsation is greater than usual, and it is called small or contracted under the opposite con dition. Fullness may depend on general plethora and on prolonged and forcible contractions of the left ventricle of the heart; a small pulse results from general deficiency of blood, from feeble ac tion of the heart, congestion of the venous sys tem, or exposure to cold. When very small it is termed thread-like.
The tension or hardness of the pulse is the property by which it resists compression. A hard pulse can scarcely be stopped by any degree of pressure by the finger. Hardness is favored by a powerfully acting heart, a normal amount of blood, and contraction of the peripheral blood ves sels, as for instance by cold. Softness of the pulse is favored by a feeble heart, by valvular im perfections interfering with the supply of blood to the arterial system, and by a free flow through the capillary area. A hard pulse is generally in dicative of inflammation, and a soft or compressi ble pulse of general weakness.
The blood from the veins returns to the heart under normal conditions in a steady stream, the pulse being lost in the capillary area. Some pulsation, however, can often be seen in the larger veins near the heart, the jugular veins, for example, in many persons with a healthy circulation. The expansion of the vein is syn chronous with dilatation of the ventricles, and collapse with contraction. Another kind of pul sation, in which this relation is reversed, takes place when the tricuspid valves guarding the veins become insufficient through disease. A wave of blood is sent back into the venous trunks, producing a riiible pulsation. This phenomenon may also be produced by hypertrophy of the right auricle and aneurism of the aorta.
An instrument has been devised by which the variations of the pulse can he indicated upon paper attached to a revolving cylinder. See SPHYGMOGRAPH; HEART, DISEASES OF TIIE; AR TERIES, paragraph Diseases.