This name is given to small bodies composed of very combustible matter, which are burned in contact with the skin. The remedy has been in use from time immemorial in China and Japan, whence it was carried to Europe by the Portuguese. Brought into extraordinary credit, some years since, by the countenance of Larry and others, it has since declined much in popularity, and is now, I believe, comparatively little used, though no doubt susceptible of occasional beneficial application.

Moxa is in the form of cones or cylinders, which are made of various material. Perhaps the kind most used consists of cylinders of cotton impregnated with nitre, and enclosed in linen or silk. The advantage of this substance is that, after having been set on fire, it will continue to burn spontaneously, without the necessity of being blown upon, by a pair of bellows or otherwise, to support the combustion. For the precise mode of preparing this and other forms of moxa, the reader is referred to the U. S. Dispensatory.

Moxa may be so used as to produce either a rubefacient, vesicatory, or escharotic effect, according to the extent to which the combustion is permitted to proceed, and acts therapeutically upon the same principles as those which govern these several classes respectively. it is, however, in general so applied as to form an eschar. The complaints in which it has been most employed are obstinate neuralgia; chronic inflammation of the spine and hip, and other obstinate scrofulous and rheumatic affections; paralytic diseases, as amaurosis, deafness, loss of taste, muscular palsy, etc.; and chronic internal inflammations, as of the bronchia, pleura, liver, and spleen. But it may be used whenever a strong and sustained revulsive impression is indicated, and no danger exists of local injury from the application. Wherever the skin has beneath it little cellular or adipose tissue, and lies immediately over bone, tendons, or cartilage, it should be avoided; as over the cranium where protected only by the periosteum and skin; the eyelids, nose, and ears; the larynx and trachea; the spinous processes of the vertebrae; the projecting parts of joints; or near the tendons of the wrist, ankle, hands, and feet. it should not be applied over the mamma or testicle, along the spermatic cord, or in positions in which it might endanger an opening into the joints.

The cylinder used may be from half an inch to an inch in diameter, and at most an inch high. One end of it being set on fire, the other is placed on the skin, and held there by means of a pair of forceps or otherwise. in order to avoid injury of surrounding parts, they may be covered with moistened pasteboard or a compress of linen, with a hole cut in the centre so as to fit the cylinder. if necessary, the combustion may be supported by blowing on it with the breath through a tube, or by a pair of bellows.

The sensation excited by it differs from that of the red hot or incandescent iron, in being slight at first, and gradually increasing in intensity, till it becomes exceedingly severe; while, from the latter cause, it is severest at first and gradually declines. if a rubefacient impression only is desired, the moxa may be allowed to burn for a short time only; if a full effect, to burn till it is consumed. The extent and depth of the eschar will of course be proportionate to the size of the cylinder, and the amount and nature of the material contained in it. The skin beneath the moxa is left yellowish, dry, and hard, with an areola of redness around it, which, however, soon disappears. Several days usually elapse before the eschar begins to be detached. its beneficial effects depend mainly on the suppuration of the resulting ulcer, which, if thought desirable, may be kept up by issue peas.