Smallpox (variola), a contagious fever, characterized by a pustular eruption having a depressed centre. The terms variola and paccc first occur in the Bertinian chronicle of the date 961. Variola is derived from the Latin varus, a blotch or pimple, while pox is of Saxon origin and signifies a bag or pouch; the prefix small was added in the 15th century. The era commonly assigned for the first appearance of smallpox is A. D. 569; it seems then to have begun in Arabia, and the raising of the siege of Mecca by an Abyssinian army is attributed to the ravages made by smallpox among the troops. The new part which Arabia under Mohammed and his followers was made to play in history contributed to the rapid propagation of the disease throughout the world. Rhazes, an Arabian physician who practised at Bagdad about the beginning of the 10th centurv, is the first medical author whose writings have come down to us who treats expressly of the disease; he however quotes several of his predecessors, one of whom is believed to have flourished about the year of the Hegira, A. D. 622. Measles and scarlet fever were at first confounded with smallpox, or considered as varieties of it; and this error seems to have prevailed more or less until Sydenham finally showed the essential differences between them.

Boerhaave was the first to insist that contagion is essential to the propagation of the disease. - The period of incubation, that is, the time that elapses from the moment the patient receives the contagion until it begins to manifest its effect in the initiatory fever, is usually 14 days, though it sometimes varies. During this time there is usually no disturbance of the ordinary health.

The invasion of the disease is announced by chills followed by fever; this is apt to be attended with pain in the back, particularly in the loins, and with nausea and vomiting. If the fever runs high, with violent pain in the back and much delirium, the disease commonly assumes a severe form. In children the invasion is often announced by an attack of convulsions. The eruption begins to show itself on the third day of the fever. As a rule, it appears first on the face, then on the neck and wrists, then on the trunk, and finally on the extremities. On the fifth day the eruption is complete, and after this few or no new spots appear. It at first consists of minute rounded papules or pimples of a characteristic solid consistency, feeling like small shot beneath the skin. It is by this peculiar solidity of the spots that smallpox at this period is distinguished from other papular eruptions. By the fourth day from their first appearance the papules are converted into vesicles filled with a thin lymph and having a depressed centre, whence they are termed umbilicated.

The vesicles begin now to be surrounded by an areola, or circular flush upon the skin, which soon becomes dark crimson; the lymph, at first colorless and transparent, is gradually converted into pus, which increases in quantity and distends the vesicles until they become hemispherical. About the eighth day of the eruption a dark spot makes its appearance at the centre of the pustule, and gradually dries up and is converted into a scab. When this scab falls it leaves either an indelible cicatrix or a purplish red mark which fades very slowly, and which long exposure to a cool atmosphere renders very distinct. In passing away, the eruption follows the course which it took on its first appearance, the scabs first falling from the face, then from the trunk, and last from the extremities. - When the pustules are comparatively few, they are separated, sometimes widely, from each other, and the disease is termed discrete (variola dlscreta); when they are very numerous, they touch each other and run together, and then it is termed confluent (variola confluens); and between the two a third variety, the semi-confluent or coherent, is often spoken of.

In the discrete form the fever commonly subsides on the appearance of the eruption, and when the pustules are few it may not return; but where they are at all numerous, their maturation is commonly attended with more or less fever. With the appearance of the eruption on the surface, more or less sore throat is complained of; the fauces and tonsils are red and swollen, and pustules make their appearance upon them, upon the roof of the mouth, and the inside of the cheeks; the patient at the same time is commonly troubled with salivation. When smallpox is confluent, the subcutaneous cellular tissue seems involved in the disease, the swelling is very great, and by the fifth day the patient is commonly unable to open his eyes. The eruption on the face sometimes coalesces into one huge sore; it is attended with a tormenting itching, and the fever is of the typhoid kind, the debility being extreme, and the patient restless, sleepless, and often delirious, while the pulse is small, frequent, and feeble. In such cases the accompanying inflammation of the mouth, nasal passages, pharynx, and larynx adds greatly to the distress of the patient and the danger of the disease, sometimes even producing suffocation.

The disease is always attended by a peculiar odor, but in confluent cases this is nauseous and offensive to an excessive degree. In this form the fever, which commonly abates on the coming out of the eruption, is aggravated as the eruption approaches maturation. The eighth day of the eruption or the eleventh of the disease is commonly the most fatal day, while more patients die during the second week of the disease than either earlier or later. A second attack, even after free exposure to the contagion, is very rare. Only widely separated instances have been known. - When patients recover from severe attacks of smallpox, blindness from an intercurrent inflammation of the conjunctiva is an occasional result, and before the general introduction of vaccination blindness from smallpox was common. Besides inflammation of the eyes, glandular swellings and abscesses, bed sores, and phlebitis are occasional complications. It is also sometimes complicated with a diseased condition of the blood, produ-. cing haemorrhage from various organs, together with petechiae. These cases are always attended with great debility; the accompanying fever is typhoid, and the eruption itself does not come out freely. They are almost invariably fatal. Pregnancy is a serious complication.

Abortion or premature delivery with the death of the child is commonly produced, but the mother frequently recovers. Sometimes the child presents the characteristic eruption of the disease, but this is rare. Still more rarely a mother whose system has been protected by vaccination or a previous attack of the disease, communicates it, after exposure, to the foetus in utero, while she herself escapes. Confluent smallpox is always dangerous, and the danger is aggravated if the patient be still in infancy or over 45 years of age, or of a feeble or strumous constitution. - The mortality from smallpox is estimated at one fourth or one fifth of all who are attacked; that of the London smallpox hospital has long averaged 30 per cent. Like many other contagious diseases, it is subject to epidemic influence, and when it prevails epidemically it seems to be severer and more fatal. It is remarkable that when it is communicated by a minute portion of the virus being inserted under the cuticle by inoculation, as it is termed, the disease is far less violent than if communicated through the atmosphere; and yet a second attack in such a case is as improbable as in any other.

When patients are inoculated the mortality is rarely greater than 1 in 600 or 700. Inoculation was introduced into civilized Europe from Constantinople through the sense and courage of Lady Mary Wortley Montagu, but since the discovery of vaccination by Dr. Jenner has been discontinued. (See Vaccination.) - For a long time the dangers of smallpox were aggravated by the means used for its cure; in accordance with the theories of the time, which still have their influence among the vulgar, the eruption was looked upon as an effort made by nature to free the system of morbid matter; the more abundant it was, the better for the patient. The eruption was accordingly encQuraged by warm drinks and a heated atmosphere. Sydenham was the first to inculcate the necessity of free ventilation and a cooling regimen. Mild cases require little except attention to hygienic measures; the disease is attended with little danger, and should run its course uninfluenced by art. When it is severe, attention should be early directed to supporting the strength of the patient. The diet should be as nutritious as he can bear, and, when indicated by the pulse, wine and stimulants should be freely administered.

The troublesome itching, which causes great suffering, may be alleviated by the application of sweet oil, cold cream, or lard; opiates may be useful to procure sleep, and the bowels should be occasionally moved by mild laxatives or enemata.