It was observed that those persons who were habitually exposed to the cool air, were less liable to the disease than others. I ascribe it to the habitual impression of the cool night air upon the bodies of the city watchmen, that but four or five of them, out of twenty-five, were affected by the disease.
After the body had been heated by violent exercise, a breeze of cool air sometimes excited the disease in those cases where there had been no change in the temperature of the weather.
7. Sleep. A great proportion of all who were affected by this fever, were attacked in the night. Sleep induced what I have called debility from abstraction, and thereby disposed the miasmata which floated in the blood, to act with such force upon the system as to destroy its equilibrium, and thus to excite a fever. The influence of sleep as a predisposing, and exciting cause was often assisted by the want of bed-clothes, suited to the midnight or morning coolness of the air.
8. Immoderate evacuations. The efficacy of moderate purging and bleeding in preventing the disease, led some people to use those remedies in an excess, which both predisposed to the disease, and excited it. The morbid effects of these evacuations, were much aided by fear, for it was this passion which perverted the judgment in such a manner, as to lead to the excessive use of remedies, which, to be effectual, should only be used in moderate quantities.
The disease appeared with different symptoms, and in different degrees, in different people. They both varied likewise with the weather. In describing the disease, I shall take notice of the changes in the symptoms, which were produced by changes in the temperature of the air.
The precursors, or premonitory signs of this fever were, costiveness, a dull pain in the right side, defect of appetite, flatulency, perverted taste, heat in the stomach, giddiness, or pain in the head, a dull, watery, brilliant, yellow, or red eye, dim and imperfect vision, a hoarseness, or slight sore throat, low spirits, or unusual vivacity, a moisture on the hands, a disposition to sweat at nights, or after moderate exercise, or a sudden suppression of night sweats. The dull eye, and the lowness of spirits, appeared to be the effects of such an excess in the stimulus of the miasmata as to induce depression, while the brilliant eye, and the unusual vivacity, seemed to have been produced by a less quantity of the miasmata acting as a cordial upon the system. More or less of these symptoms frequently continued for two or three days before the patients were confined to their beds, and in some people they continued during the whole time of its prevalence in the city, without producing the disease. I wish these symptoms to be remembered by the reader. They will form the corner stone of a system which I hope will either eradicate the disease altogether, or render it as safe as an intermitting fever, or as the small-pox when it is received by inoculation.
Frequent as these precursors of the fever were, they were not universal. Many went to bed in good health, and awoke in the night with a chilly fit. Many rose in the morning after regular and natural sleep, and were seized at their work, or after a walk, with a sudden and unexpected attack of the fever. In most of these cases the disease came on with a chilly fit, which afforded by its violence or duration a tolerable presage of the issue of the disease.
Upon entering a sick room where a patient was confined by this fever, the first thing that struck the eye of a physician was the countenance. It was as much unlike that which is exhibited in the common bilious fever, as the face of a wild, is unlike the face of a mild domestic animal. The eyes were sad, watery, and so inflamed, in some cases, as to resemble two balls of fire. Sometimes they had a most brilliant or ferocious appearance. The face was suffused with blood, or of a dusky colour, and the whole countenance was downcast and clouded. After the 10th of September, when a determination of blood to the brain became universal, there was a preternatural dilatation of the pupil. Sighing attended in almost every case. The skin was dry, and frequently of its natural temperature. These were the principal symptoms which discovered themselves to the eye and hand of a physician. The answers to the first questions proposed upon visiting a patient, were calculated to produce a belief in the mind of a physician, that the disease under which the patient laboured was not the prevailing malignant epidemic. I did not for many weeks meet with a dozen patients, who acknowledged that they had any other indisposition than a common cold, or a slight remitting or intermitting fever. I was particularly struck with this self-deception in many persons, who had nursed relations that had died with the yellow fever, and who had been exposed to it in neighbourhoods where it had prevailed for days and even weeks with great mortality. I shall hereafter trace a part of this disposition in the sick to deceive themselves to the influence of certain publications, which appeared soon after the disease became epidemic in the city.
In the further history of this fever, I shall describe its symptoms as they appeared,
I. In the sanguiferous system.