Contagious diseases propagate among those who expose their persons to contact with the matters or clothes impregnated with them. There are many facts of an incontrovertible character, which prove the occasional operation of the former mode at least, and to render probable, that of the latter; and hence, whatever attention is paid to cleanliness of the sick person, his apartment, and to the prevention and removal of vitiated air, persons touching a body, when there is present on its surface specific contagious poison, such as the matter of small-pox, or even handling clothes, which have become impregnated with it, incur a risk of being affected with the same disease, by means of that matter or fomitic contagion. In all the contagious diseases (those in which there is eliminated a palpable poison, or matter capable of causing the same disease in others), their respective matters are invariably formed, and are apt to propagate in the modes specified, so that visitors and other attendants should ever be upon their guard, the first not to touch the sick person at all, and the latter not to touch more than is necessary, and to take precaution to render the risk as slight as possible. Subjoined is a list of diseases which are known to be contagious, or to be possessed of a matter of the nature referred to, and that are therefore wont to be propagated by contact with the sick, or with his clothes. Small-Pox. Scarlet Fever. Measles. Chicken-Pox. Cow-Pox. Itch. Plague. Porrigo. &c. These are almost the only diseases known in this country, which are positively ascertained to be characterized by the elimination of contagious matter, and which, therefore, there is any risk of getting by contagion. The continued fever of this country has been supposed, by some physicians, to be a contagious disease, from there being sometimes observed pimples on persons affected with it; but that is by no means an ascertained point. Those above enumerated seem to include all the most important diseases in this country, which are capable of being propagated by contagion, acting in either of the two ways already described. Some of them are capable of affecting the same individual only once, and some affect persons as often as they are exposed to their specific contagious matters. How comparatively small, then, is the range of contagion,—an agent which has been thought to accomplish worlds of mischief, and to destroy almost whole communities. Visitors may approach within a very short distance of persons afflicted with these distempers, without danger of suffering, provided they do not touch the bodies or the clothes.