VACCINATION is the process by which a specific disease, termed vaccinia, or cow pox (from the Latin word 'caeca, a cow), is introduced into the human organism with the view of protecting it against an attack of an incomparably more severe disorder—viz., smallpox. For the history of this remarkable discovery of vaccination—" that mas ter-piece of medical induction"—we must refer to the life of Jenner (q.v.). In his Inquiry into the Causes and Effects of the Varioler Vaccince, published 1798, he established the following facts: (1) That this disease casually communicated to man has the power of rendering him unsuseeptilde of small-pox: (2) that the specific 'cow-pox alone, and not other eruptions affecting the cow, which might be confounded with it, had tins pro tective poWer; (3) that the cow-pox might be communicated at will from the cow to man by the hand of the surgeon, whenever the requisite opportunity existed; and (4)i that the cow-pox once engrafted on the human subject, might be continued from indi vidual to individual by successive transmissions, conferring on each the same immunity from small-pox as was enjoyed by the one first infected direct from the cow.
The method of vaccinating and the phenomena of as observed in the human subject after vaccination, claim our first and chief attention. Except under circum stances of special risk (as, for instance, where small-pox is in the neighborhood), children should only be vaccinated when they are in apparently good health. Diarrhea and skiu diseases are especially to be avoided; and it is important to see that there is no chafing behind the ears, or in the folds of the neck or groin. As more than one-fourth of the whole number of deaths from small-pox in England during the six consecutive years 1856-61, took place in children of less than one year, it is obviously expedient. that children should be vaccinated in very early infancy, provided health permits. Dr. Seaton, in his comprehensive article on this subject in Reynold's System of Medicine (1866, vol. i. p. 489), observes that " plump and healthy children living in large towns should be vaccinated when a month or six weeks old; in more delicate children, the vaccination might be postponed till they are two or three months old; but all, except those whose state of health positively contra-indicates vaccination, should be vaccinated by the age of three months." This early age has also the advantage of being free from. the irritation of teething.
The lymph to be used should always be taken from a healthy child, and from thoroughly characteristic vesicles; and when lymph in all respects satisfactory cannot be procured as is often the case in country districts, the operation should be postponed. Lymph is usually taken when the vesicle is fully formed, which is usually about a week after vaccination; if it is not taken till the areola (which will be presently described). is complete, its protective power is far less certain. " Prime lymph," says Dr. Seaton, "has always a certain degree of viscidity; and a thin serous lymph, even from a vesicle which is not advanced, is to be avoided. Babies are much better lymph-givers than elder children or adults; and children of dark complexion, not too florid, with a thick, smooth, clear, skin, yield the finest and most effective lymph." Lymph should always, if practicable, be passed direct from arm to arm; and preserved lymph should only be had recourse to when a vhccinated child cannot be obtained. A good vesicle freely punctured on its surface exudes enough lymph or vaccine matter for the direct vacina tion of five or six children, and for charging six or eight ivory points for future emer gencies. The process of vaccination consists essentially in introducing the lymph into the structure of the true skin, or in bringing it in contact with the absorbing surface. This
may be effected in various ways, one of the most common being by puncture. As the operation is extremely simple, and the knowledge of the mode of performing it may prove useful to many of our colonial readers, we shall briefly describe it. The skin on the out side of the arm, below the shoulder, should be held upon the stretch, and a very sharp, clean lancet, well charged with lymph, should be made to puncture the skin from above downward, at an angle of about 45°, and be made just to enter the true skin. The matter thus inserted is retained by the valvular character of the puncture and the elasticity of the skin. In this form of the operation, not less than five or six such punctures should be made, at a distance of half an inch from the other; and for the sake of security, three punctures may be made on each arm. If the :ymph is preserved on points, each point, after being held in the steam of hot water so as to dissolve the lymph, should be in serted into the punctures made by an ordinary lancet. Some surgeons make a number of minute superficial punctures over a patch of the size of a fourpenny-piece, and spread the lymph over this spot with the flat part of the lancet: this kind of tatooing should be repeated on three spots. Others make a number of parallel scratches, or crossed scratches, with a charged lancet; and others, again, use special scariflers or rakes, con sisting of three or four needle-points inserted in an ivory handle; and drawn either once or again at right angles over the tense skin, the lymph being then plastered over the scarified surface. Of these various plans, Dr. Seaton believes that the best marks and most successful treatment result from this last plan of cross scratches. A far better plan of preserving lymph than that of drying it on points, is that of preserving it in a fluid state in Husband's closed capillary tubes, in which form it is ready for use without any preparation. When the operation is successfully performed, the skin at the spot becomes slightly elevated, hard, and red on the third or fourth day; on the fifth or sixth day a vesicle of a blueish-white color forms, which presents an elevated edge and a depressed cup. It is distended with clear lymph, and attains its perfection on the eighth day; and now, or on the ninth day, the vesicle is surrounded by an inflamed ring or arcola; on the ninth, tenth, and eleventh days the vesicle becomes a pustule, the cupped form disappears, the areola enlarges till it becomes a circle, with a diameter of from one to three inches. On the twelfth, thirteenth, and fourteenth days the pustule dries up; and in the course of the next week the scab separates and falls off; it seldom remains so long as the twenty-fifth day. It leaves a cicatrix, which commonly is perma nent in after-life, circular, somewhat depressed, dotted or indented with minute pits, and in some instances radiated. The establishment of the areola is accompanied with constitutional disturbances, as indicated by restlessness and heat of skin, frequent derangement of the stomach and bowels, and occasional swelling of the glands of the arm-pit. These symptoms arc seldom severe, but seldom quite absent. We meet with cases in which the course of the above symptoms is modified, as when they are simply retarded, or simply accelerated, or altogether irregular and spurious; and it should be carefully borne in mind that " a vaccination presenting any deviation from the perfect character of the vesicle and the regular development of the areola, is not to be relied on as protective against small-pox."—Seaton, op. cat. As a general rule, neither the local nor the constitutional symptoms of ordinary vaccination require any treatment.