It appears probable that vitiated air, unlike the palpable contagious poisons, assists in the production of that disease only which is prevailing, or to which there exists a disposition from the operation of other agencies; and it appears probable that vitiated air, whether it arises from persons affected with this or that disease, will, within certain limits, produce one disease as readily as another, the required particular disposition being present; for instance, that the effluvia from a small-pox patient will induce small-pox or typhus fever, according as there exists a disposition to the one disease or the other, and _vice versa_. The effluvia arising from newly opened graves have been often productive of putrid fever. The following case will shew that effluvia arising from the remains of a person who died of consumption of the lungs, and not of small-pox, produced that disease, viz. small-pox. When that case occurred, small-pox was prevailing, and doubtless, had there been existing at the time a disposition to putrid fever, that disease, and not small-pox, would have been induced by the effluvia which arose from the grave. In September 1834, Peter Macawley, about twenty-eight years of age, gardener and grave-digger, was employed in the churchyard of Tranent. While busily digging a grave, he unexpectedly struck a coffin with his spade, and broke it open. The coffin contained the remains of an old woman, who had died of consumption of the lungs, and who had been interred about fourteen months. There immediately issued from the coffin the most offensive effluvia, which threatened suffocation, and made him feel very unwell. He proceeded home, and continued throughout the night very poorly, giddy, and uncomfortable. He rose next morning, and although no better, proceeded to the churchyard, gave some directions, and returned home, feeling giddy and unsteady. He was put to bed, and passed a very uncomfortable night. Called in next morning to prescribe for him, I found him to be affected with severe pain of head, great heat and sweating of skin, and great quickness of pulse. He complained of thirst, could take no food, and was occasionally delirious. On the third day of his illness, pimples appeared over the whole surface of the body, which gradually becoming larger, assumed the form of small-pox. The pocks or pustules did not mature or fill with matter in the usual way, but continued throughout to be flat, and assumed a dark blue or inky colour. His strength fast declined,—he became very low,—muttered incoherently to himself, and symptoms of a putrid character supervening, and the energies of the system fast failing, he died insensible about the twelfth day of his illness, of the worst form of immature, putrid, confluent small-pox I had ever witnessed.