Their case produces the usual effect, demands the exertion of night watching, spoken of already, as favourable to the accession of disease, and their house or apartment, close and confined as it usually is in that rank of life, becomes the abode of many unwholesome influences, and among others, of an atmosphere, deprived in a great degree of its more essential part, and loaded, too, with foreign gases, and even perhaps with chemical compounds of a virulent character, the products of putrefaction. If disease spreads much among those thus exposed, it seems fair to attribute the occurrence to these agencies known to be present, and known to be favourable to the production of sickness, and not to atmospheric contagion, as is almost universally done. The case of disease appearing in a house previously healthy, after receiving one just recovered of disease, which it is by the way consonant with our experience to say, is much more rare than the other, or that of persons actually ill,—is occasionally noticed, and the explanation, perhaps, is, that the clothes may retain impurities acquired during the course of disease, and may on this occasion shew their activity. CHAPTER IV. THERE IS NO EVIDENCE THAT ATMOSPHERIC CONTAGION TRAVELS, OR IS COMMUNICATED FROM ONE PLACE TO ANOTHER. The question of the communication of atmospheric contagion from one place to another has almost universally, on occasions of pestilence, been much agitated, in respect to individual diseases, but seldom in a comprehensive way, embracing all diseases. We propose to inquire generally into the facts which are held to prove the principle of dissemination from one place to another—whether contagious atmosphere is transmitted from one country to another, from one town to another, and from hamlet to hamlet. In the many works written by medical men on occasions of great epidemic disease, descriptive of the character of the prevalent distemper, there almost universally appear the most minute accounts of the route pursued by contagion, both fomitic and atmospheric, down to the noting of the very road, the very street or alley by which it reached a town—and of the manner in which it arrived, whether on the rags of a tattered beggar, or seated in a stage-coach.