Vaccination

(vāk-sin-a's hun.) [From L. vaccinus, belonging to cows.] (Med.) The artificial production of a disease known as the cow-pox, by inserting some of the matter of the disease under the skin, with the view of protecting it against the incomparably more severe disease called small-pox. It was proposed by Dr. Jenner, in 1798. Small bluish vesicles, surrounded by inflammation, elevated at the edge, and depre ed at the centre, and containing a limpid fluid, occasionally appear on the teats of the cow, the animal being, at the same time, somewhat indisposed. This disease, transferred to the hands of the milkers, was found, in many cases, to preserve from small-pox. A disease of the horse's head, called grease, communicated to the hands of farriers, seems to have produced the same effect. The matter from the cow is, however, the most certain; and that which it produces in one human subject may be succe fully transferred to another; though it is probable that it loses its efficacy by being transmitted too many times. In doubtful cases, the vaccination should be repeated; its repetition, even though unnece ary, can be attended with little inconvenience. [s. 926]