Yellow fever is a specific, infectious, and communicable disease of one febrile paroxysm.
This definition includes some of the most prominent characteristics of the disease. The malady, however, derives its name from a symptom not mentioned in the definition. The yellow color of the skin and scleroticæ which appears in advanced stages of grave cases of yellow fever, and which becomes especially marked in the cadaver, has ruled its nomenclature. Whatever objections may be urged against the term "yellow fever" as being founded upon a symptom of the disease not always present, it is too strongly fixed in both medical literature and popular usage to justify efforts to change it.
Neither is it liable to beget confusion as long as it is understood that it is to be restricted in its application to a specific fever induced by a specific poison, and that as an incident of its morbid process it produces yellow coloration of the surface so frequently as to suggest the prefix yellow to its title.
ETIOLOGY AND SYMPTOMATOLOGY.—In this day of almost general belief in the theory which holds that each specific disease has its own specific poison or morbific germ, it is scarcely expedient to occupy much space in discussing the propriety of classing yellow fever among the specific maladies.
Whether we rest the decision of this question upon the uniformity of those circumstances and conditions which originate and develop epidemics of yellow fever, or upon the sameness of its symptomatic phenomena wherever observed, we find very nearly as substantial claims to a specific individualization of the disease as any one of the eruptive fevers possesses. Not only are its morbid phenomena so characteristic that even non-professional observers designate it by such epithets as Bronze John, Yellow Jack, Vomito Prieto, etc., but it is inconvertible with other specific affections. This inconvertibility of yellow fever with other diseases is absolute, and affords irrefrangible evidence of the specificity of that germ or poisonous principle which produces it.
The study of yellow-fever poison after the objective method has hitherto been unproductive of definite results. When such experienced and truthful observers as Sternberg, Woodward, and Schmidt, working with the most approved microscopes, have failed to identify any organism or object peculiar to the products from the bodies of yellow-fever subjects or to the circumfusa of the sick, this declaration is sufficiently supported.
But when we turn to a subjective method of investigating that toxic agent which causes yellow fever, it is found to possess sufficiently well-marked characteristics to justify practically valuable conclusions. Some of these characteristics or modes of behavior merit notice.
1st. The human system is a field of reproduction and multiplication of yellow-fever poison. This is sufficiently established by two facts:
(a) A person in the incubative stage of yellow-fever intoxication may be divested of all fomites and yet originate other cases after a developed attack.