The Fabaceae include herbs, shrubs, and trees distributed throughout the world in a great variety of forms. Arboreal species occur in temperate and, frequently, in tropical zones, where epiphytic and climbing forms also thrive. Many leguminous shrubs and trees inhabit desert and semiarid regions, usually forming the characteristic vegetation—e.g., the acacias of the S African bushveld and of Australia, and the mesquite of the American Southwest.
Economically, the family is second only to the grasses in importance. Legumes provide valuable and nutritive foods because the food stored for the embryo in the seed (e.g., the pea) is rich in protein. In many regions, especially where meat is scarce or expensive, legumes—notably peas, beans, lentils, peanuts, carob, and soybeans—are staples of the diet. The Fabaceae are equally important as fodder and forage plants; clover, alfalfa, vetch, lupine, beggarweed, lespedeza, sainfoin, and soybeans are among the numerous valuable types.
These food and forage legumes are chief among the plants used as "green manure" (see manure). Nitrogen-fixing bacteria dwelling in nodules of the roots of most legumes fix free nitrogen from the air into the nitrogenous compounds needed by all forms of life for building proteins (see nitrogen cycle). Rotation of leguminous crops with nonleguminous crops has long been a standard agricultural practice; the soil is enriched when their roots are left to decay after harvesting.
The pulse family also provides gums and resins (e.g., tragacanth, copal, and acacia and carob gums), dyes and tannins (e.g., from the indigo plant, logwood, brazilwood, and types of acacia and broom), timber (e.g., rosewood, locust, honey locust, and acacia), medicines (e.g., from tamarind, licorice, and senna), perfume oils (e.g., from acacia, black locust, broom, and sweet pea), vegetable oils (e.g., soybean and peanut oils), and other commercial items such as flavorings, fibers, and insecticides.
In many parts of the world native species of the Leguminosae are of great importance locally, if not commercially. Often every part of the plant finds some use: the pods and leaves for food, beverages, and forage; the wood and stems for building purposes, fiber, and household items; and the leaves, blossoms, and bark for domestic remedies. The blossoms of many of the Leguminosae are excellent honey sources. Species that grow in arid climates are particularly valuable because of the scarcity of other fodder, food, and timber crops; they are also important to wildlife for forage and cover. Native Americans have cultivated bean plants since antiquity and still rely on breadroot, redwood, mesquite, and many other species for food and other products.
Among the native North American trees cultivated for shade or for their beautiful springtime blossoms are the locusts, the honey locust, the yellowwood, the redbud, and the acacias. The mimosas, sennas, laburnums, poincianas, Old World acacias, shrubby brooms, and wisteria have been introduced for the same purpose. The American lupines, the Old World sweet pea, and numerous types of clover are among the cultivated herbaceous species. In all, members of over 140 genera of the Leguminosae are grown for ornament. Furze from Europe and the kudzu vine from Asia have been introduced for erosion control (the latter has become a noxious weed). The locoweeds and lupines of the western states are among the plants poisonous to livestock.
See articles on individual plants.
The pulse family is classified in the division Magnoliophyta, class Magnoliopsida, order Rosales.
Pressure wave in the arteries from contraction of the heart. It can be felt where arteries are near the skin's surface; it is usually read at the carotid artery in the neck or at the wrist. Its rate, strength, and rhythm and the contour of the wave provide valuable information but must be viewed in context (e.g., rapid pulse occurs with serious heart disease, simple fever, or vigorous exercise). The average adult pulse rate is 70–80 beats per minute; the rate decreases with age and is generally faster in women.
Learn more about pulse with a free trial on Britannica.com.
In medicine, a person's pulse is the throbbing of their arteries. It can be felt in any place that allows for an artery to be compressed against a bone, such as at the neck (carotid artery), at the wrist (radial artery), behind the knee (popliteal artery), on the inside of the elbow (brachial artery), and near the ankle joint (posterior tibial artery). The pulse rate can also be measured by measuring the heart beats directly (the apical pulse).
Pressure waves move the artery walls, which are pliable; these waves are not caused by the forward movement of the blood. When the heart contracts, blood is ejected into the aorta and the aorta stretches. At this point, the wave of distention (pulse wave) is pronounced but relatively slow-moving (3–6 m/s). As it travels towards the peripheral blood vessels, it gradually diminishes and becomes faster. In the large arterial branches, its velocity is 7–10 m/s; in the small arteries, it is 15–35 m/s. The pressure pulse is transmitted fifteen or more times more rapidly than the blood flow.
Pulse is also used, although incorrectly, to denote the frequency of the heart beat, usually measured in beats per minute. In most people, the pulse is an accurate measure of heart rate. Under certain circumstances, including arrhythmias, some of the heart beats are ineffective, and the aorta is not stretched enough to create a palpable pressure wave. The pulse is too irregular and the heart rate can be (much) higher than the pulse rate. In this case, the heart rate should be determined by auscultation of the heart apex, in which case it is not the pulse. The pulse deficit (difference between heart beats and pulsations at the periphery) should be determined by simultaneous palpation at the radial artery and auscultation at the heart apex.
A normal pulse rate for a healthy adult, while resting, can range from 60 to 100 beats per minute (BPM), although well-conditioned athletes may have a healthy pulse rate lower than 60 BPM. Bradycardia occurs when the pulse rate is below 60 per minute, whereas tachycardia occurs when the rate is above 100 BPM. During sleep, the pulse can drop to as low as 40 BPM; during strenuous exercise, it can rise as high as 150–200 BPM. Generally, pulse rates are higher in infants and young children. The resting heart rate for an infant is usually close to an adult's pulse rate during strenuous exercise (average 110 BPM for an infant).
A collapsing pulse is a sign of hyperdynamic circulation.
The ease of palpability of a pulse is dictated by the patient's blood pressure. If his or her systolic blood pressure is below 80 mmHg, the radial pulse will not be palpable. Below 70 mmHg, the brachial pulse will not be palpable. Below 60 mmHg, the carotid pulse will not be palpable. However, a study by the National Institutes of Health indicated that this method was not accurate enough and often overestimated a patient's systolic blood pressure. The lack of a palpable carotid pulse is often an indication of death.
Pulses are manually palpated with fingers. When palpating the carotid artery, the femoral artery or the brachial artery, the thumb may be used. However, the thumb has its own pulse which can interfere with detecting the patient's pulse at other points, where two or three fingers should be used. Fingers or the thumb must be placed near an artery and pressed gently against a firm structure, usually a bone, in order to feel the pulse.
Make sure the person is calm and has been resting for 5 minutes before reading the pulse. Put the index and middle fingers over the pulse count, and count for 30 seconds, and afterwards multiply by 2, to get the pulse rate. If the person's pulse rate is irregular, count for a full minute, and do not multiply. Averaging multiple readings may give a more representative figure.
Home blood pressure measurement devices also typically give a pulse reading.