Measles (Rubeola Rnorbilli), a contagious exanthematous fever, attended with a characteristic eruption. Up to the latter part of the last century measles and scarlet fever were confounded together, or at least were esteemed, like simple and confluent smallpox, to be mere varieties of a common disease. Measles commences with the ordinary symptoms of fever, chilliness, loss of appetite, and lassitude, succeeded by heat of the skin, thirst, and frequency of pulse; but in addition to these, the attack is almost invariably attended with inflammation of the mucous membrane lining the air passages; the eyes are red and watery; there is defluxion from the nostrils, hoarseness, and cough. The eruption commonly appears on the fourth day, at first about the head and neck, then the trunk and arms, and finally reaching the lower extremities; it takes two or three days to complete its course, and when it reaches the feet and legs has often begun to disappear from the face. The eruption consists of little papules, somewhat resembling flea bites, of a dark red color, which as they coalesce at their edges assume an irregularly crescentic form. The period of incubation, that is, the time elapsing from exposure to the contagion to the time of attack, is put down as from seven to fourteen days.

All ages are liable to it, though infants at the breast are not so apt to be attacked as those somewhat older. It often shows itself in newly recruited regiments, spreading from one individual to another so rapidly as to assume the form of an epidemic. The disease is not commonly dangerous, though when introduced into the Pacific islands, some years since, it proved exceedingly fatal. When the eruption is fully out, the cough, at first dry and troublesome, generally becomes softer and less frequent; and at the end of six or seven days from the coming out of the first papules, they have disappeared. Where danger occurs, it is from inflammation of the air passages; the disease may thus become complicated with croup, or in subjects predisposed to consumption the seeds of that disease may be developed. The eyes, too, are sometimes left irritable and inflamed. In all ordinary cases, a simple diet, the maintenance of an equable temperature, and perhaps the exhibition of a mild diaphoretic or expectorant, are all that is required. - For an account of measles in swine, see Entozoa.