Sooner or later, varying from a few hours to several days, in the ordinary course of the disease, the fever subsides. From this time the patient may recover without any further symptoms, but this is, by no means, the usual result. If the subsidence of the fever is accompanied by natural pulse, a free, but not profuse or prostrating perspiration, a genial warmth of the surface, natural appearance of the countenance, eyes, and tongue, with little or no soreness on pressure over the stomach, we may safely look for a speedy recovery. But if, on the contrary, the eyes, face, and tongue, become yellow, or orange-colored, the epigastrium is tender to pressure, the urine has a yellow tinge, the pulse becomes unnaturally slow, with the least degree of mental stupor, we have reason to know, full well, that the lull of the fever is only the calm preceding a more destructive storm. The fever has subsided, only because exhausted nature could re-act no longer. It may be in a few hours, or not until twelve or twenty-four have elapsed, the pulse becomes quickened, even to the frequency of 120 to 140 in a minute, but very feeble, the extremities of the fingers and toes turn purple or dark, the tongue becomes brown and dry, or is clean, red, and cracked, sordes may be on the teeth, the stomach become more irritable, nausea and vomiting are extreme, the substances vomited being, at first, reddish, afterwards watery, containing floculæ, like soot, or coffee grounds; the breath becomes foul, and the whole surface emits a sickening odor. The pulse becomes very small, though the carotid and temporal arteries beat violently. The urine fails to be secreted, and later, blood is discharged from the mucous surfaces, involuntary discharges from the bowels, clammy sweats; and death follows.
The disease runs its course in from three to seven days, sometimes proves fatal in less than a day, and at others, assumes a typhoid form, and runs for weeks. Occasionally it sets in without any of the premonitory symptoms, the chill being first, the fever following, succeeded immediately by the black vomit, going through all the stages in a single day, or two days.
Again, it sometimes begins with the black vomit, the patient being immediately prostrated. In all cases, however it may begin, the peculiar head-ache and back-ache as described in the beginning, as well as the extreme heat of the head and face, redness of the eyes, the gnawing sensation at the stomach, and peculiar nausea are present. These seem to be characteristic symptoms that mark the Yellow Fever, and those which should guide in the search for the proper remedies.