It has been urged as an objection to the influence of powerful epidemics chasing away, or blending with fevers of inferior force, that the measles sometimes supplant the small-pox, and mild intermittents take the place of fevers of great malignity. This fact did not escape the microscopic eye of Dr. Sydenham, nor is it difficult to explain the cause of it. It is well known that epidemics, like simple fevers, are most violent at their first appearance, and that they gradually lose their force as they disappear; now it is in their evanescent and feeble state, that they are jostled out of their order of danger or force, and yield to the youthful strength of epidemics, more feeble under equal circumstances of age than themselves. It would seem, from this fact, that an inflammatory constitution of the air, and powerful epidemics, both in their aggregate and individual forms, possessed a common character. They all invade with the fury of a savage, and retire with the gentleness of a civilized foe.
It is agreeable to discover from these facts and observations, that epidemic diseases, however irregular they appear at first sight, are all subject to certain laws, and partake of the order and harmony of the universe.
The action of the miasmata upon the body, when, from the absence of an exciting cause, they did not produce fever, was the same as I have elsewhere described. The sensations which I experienced, in entering a small room where a person was confined with this fever, were so exactly the same with those I felt the year before, that I think I could have distinguished the presence of the disease without the assistance of my eyes, or without asking a single question. After sitting a few minutes in a sick room, I became languid and fainty. Weakness and chilliness followed every visit I paid to a gentleman at Mr. Oellers's hotel, which continued for half an hour. A burning in my stomach, great heaviness, and a slight inflammation in my eyes, with a constant discharge of a watery humour from them for two days, succeeded the first visit I paid to Mrs. Sellers. These symptoms came on in less than ten minutes after I left her room. They were probably excited thus early, and in the degree which I have mentioned, by my having received her breath in my face by inspecting her tonsils, which were ulcerated on the first attack of the fever. I formerly supposed these changes in my body were proofs of the contagious nature of the yellow fever, but I shall hereafter explain them upon other principles.
I recollect having more than once perceived a smell which had been familiar to me during the prevalence of the yellow fever in 1793. It resembled the smell of liver of sulphur. I suspected for a while that it arose from the exhalations of the gutters of the city. But an accident taught me that it was produced by the perspiration of my body. Upon rubbing my hands, this odour was increased so as to become not only more perceptible to myself, but in the most sensible degree to my pupil, Mr. Otto. From this fact, I was convinced that I was strongly impregnated with miasmata, and I was led by it to live chiefly upon vegetables, to drink no wine, and to avoid, with double care, all the usual exciting causes of fever.
There was another mark by which I distinguished the presence of the seeds of this fever in my system, and that was, wine imparted a burning sensation to my tongue and throat, such as is felt after it has been taken in excess, or in the beginning of a fever. Several persons, who were exposed to the miasmata, informed me that wine, even in the smallest quantity, affected them exactly in the same manner.
I attended four persons in this fever who had had it the year before.
It remains now that I mention the origin of this fever. This was very evident. It was produced by the exhalations from the gutters, and the stagnating ponds of water in the neighbourhood of the city. Where there was most exhalation, there were most persons affected by the fever. Hence the poor people, who generally live in the neighbourhood of the ponds in the suburbs, were the greatest sufferers by it. Four persons had the fever in Spruce, between Fourth and Fifth-streets, in which part of the city the smell from the gutters was extremely offensive every evening. In Water-street, between Market and Walnut-streets, many persons had the fever: now the filth of that confined part of the city is well known to every citizen.