23. The matters which usually stagnate in the gutters, common sewers, docks, and alleys of cities, and in the sinks of kitchens. A citizen of Philadelphia, who had a sink in his kitchen, lost a number of cats and dogs by convulsions. At length one of his servants was affected with the same disease. This led him to investigate the cause of it. He soon traced it to his sink. By altering its construction, so as to prevent the escape of noxious air from it, he destroyed its unwholesome quality, so that all his domestics lived in good health in his kitchen-afterwards. 24. Air emitted by agitating foul and stagnating water. Dr. Franklin was once infected with an intermitting fever from this cause. 25. A duck pond. The children of a family in this city were observed, for several successive years, to be affected with a bilious remitting fever. The physician of the family, Dr. Phineas Bond, observing no other persons to be affected with the same fever in the neighbourhood, suspected that it arose from some local cause. He examined the yard belonging to the house, where he found an offensive duck pond. The pond was filled with earth, and the family were afterwards free from an annual bilious fever. 26. A hog-stye has been known to produce violent bilious fevers throughout a whole neighbourhood in Philadelphia. 27. Weeds cut down, and exposed to heat and moisture near a house. Fevers are less frequently produced by putrid animal, than by putrid vegetable matters. There are, however, instances of their having been generated by the following animal substances in a state of putrefaction. 1. Human bodies that have been left unburied upon a field of battle. 2. Salted beef and pork. 3. Locusts. 4. Raw hides confined in stores, and in the holds of ships. 5. A whale thrown upon the sea shore in Holland. 6. A large bed of oysters. The malignant fevers which prevailed in Alexandria, in Virginia, in 1803, and in Southwark, adjoining Philadelphia, in the year 1805, were derived from this cause[11]. [11] It has been a common practice with many families, in New-York and Philadelphia, for several years past, to lay in a winter store of oysters in their cellars in the fall of the year. May not a part of these oysters, left in these cellars from forgetfulness, or from being unfit for use, become, by putrifying there, the cause of malignant fevers in the succeeding summer and autumn? 7. The entrails of fish. And,