ammonia in various states of combination,) and their superabundant acid, the ferment of the disease; and this penetrated into the lungs of the bystanders as they breathed, and provided they were but predisposed for its reception, as above stated, continually produced it. It may be considered as certain that mere manual contact was not sufficient to communicate the infection, and that this was propagated, either by the pestilential atmosphere which surrounded the beds of the sick, or by exhalations generated in unclean situations where there was no vent for their escape. On this account it was that the residence at common inns and public-houses was looked upon as dangerous[471]. I would not, however, be understood to maintain that, during the three epidemics with which, up to the present stage of our inquiry, we have become acquainted, the spread of the sweating fever alone was occasioned by infection; for if the general epidemic causes were powerful enough to excite the disease, without any previously existing poison, why might they not produce the same effect still more independently throughout the course of the pestilence, since, as is the case in all epidemics, those causes in all probability continued to increase in intensity? That the plague grew worse on the occasion of any great assemblages of the people, was at that time known, and the notion of contagion thence very naturally arose. Yet, must it here be taken into account, that even without this notion, and merely from the assemblage itself of many people in whom the like malady was germinating, and already had shewn tokens of its approach, that approach might easily be accelerated, and the disease increased among those merely slightly indisposed, by the reciprocal communication of morbid exhalations. For as the predisposition to any malady, which is an intermediate condition between that malady and the previous state of good health[472], plainly displays the properties of the disease in those whom it _threatens_ to attack, so these exhalations (or epidemic causes which give rise to Sweating Sickness in the first instance) certainly differ from those which occur in a sweating sickness which has already broken out, only in unessential respects, and might consequently stimulate the mere disposition to the disease more and more, even to the actual eruption of the disease itself. Yet a contagion was likewise in operation at the same time which was destructive even to the temperate, and to those who were apparently in health, nay, even to foreigners, who were living in an English atmosphere and on English food, as the example of the Italian Ammonius plainly proves[473].