In this case it is probable that particles of noxious animal matter progressively accumulated in the matting during the intervals between the cleansing of it; and that being set free by this operation and diffused in the atmosphere, while they were powerful enough always sensibly to affect even those who were accustomed to inhale them, were sufficiently concentrated to produce actual fever in one wholly unaccustomed to them, and rendered increasingly susceptible to their influence by recent residence in the pure air of the country; for it is remarkable that miasms sometimes act with the greatest intensity on those who habitually breathe the purest air. The miasms arising from church-yards are in general too much diluted by the surrounding air to strike the neighbouring inhabitants with sudden and severe disease, yet they may materially injure the health, and the evidence appears to me to be decisive that they often do so. Among others who sometimes obviously suffer from this cause, are the families of clergymen, when, as occasionally happens, the vicarage or rectory is situated very close to a full church-yard. I myself know one such clergyman’s family, whose dwelling-house is so close to an extremely full churchyard, that a very disagreeable smell from the graves is always perceptible in some of the sitting and sleeping rooms. The mother of this family states that she has never had a day’s health since she has resided in this house, and that her children are always ailing; and their ill health is attributed, both by the family and their medical friends, to the offensive exhalations from the church-yard. Dr. Lyon Playfair states as follows in his communication— There are two kinds of changes which animal and vegetable matters undergo, when exposed to certain influences. These are known by the terms of “decay” and “putrefaction.” Decay, properly so called, is a union of the elements of organic matter with the oxygen of the air; while putrefaction, although generally commencing with decay, is a change or transformation of the elements of the organic body itself, without any necessary union with the oxygen of the air. When decay proceeds in a body without putrefaction, offensive smells are not generated; but if the air in contact with the decaying matter be in any way deficient, the decay passes into putrefaction, and putrid smells arise. Putrid smells are rarely if ever evolved from substances destitute of the element nitrogen.