The idea that there is a scientific exactness in the employment of the clinical thermometer tends to make one overestimate its value in diagnosis.
It must be remembered that the high air temperature one encounters in the tropics affects the clinical thermometer, which is of the maximum type. This is particularly true when the sun may be shining on the container in which the thermometer may be kept. Even if one shakes down the column of mercury before putting it in the mouth, the glass of the instrument will quickly cause the mercury column again to rise. It should be a practice to place the instrument in cool water before inserting it in the mouth and we must not forget that a sufficient retention in the mouth, from two to five minutes, should be insisted upon before accepting the temperature reading.
For practical purposes we may divide tropical diseases, from a standpoint of body temperature, into two classes. (1) Those diseases in which the absence of fever in the general course of the illness is the rule, and (2) those diseases in which the presence of fever in the general course of the illness is the rule.
Nonfebrile Diseases.—Among the nonfebrile diseases we may note the following: Beriberi, sprue, pellagra, cholera, leprosy, amoebic dysentery, hookworm disease, filariasis, bilharziosis, endemic haemoptysis or paragonomiasis, liver fluke disease, malarial cachexia, yaws, verruga, oriental sore and ulcerating granuloma of the pudenda, as well as the various tropical skin diseases.
One should always keep in mind the fact that a latent malaria often gives way to frank malarial manifestations when some intercurrent disease still further reduces the body resistance. This is not infrequently the explanation of a febrile onset in the course of a disease typically afebrile. In the tropics if a fever chart does not show a characteristic periodicity one can often obtain indications of periodicity even in a continued or remittent fever course by the greater elevation of temperature every third day (tertian periodicity).
Another disease which often flares up following conditions which lower vitality and giving rise to fever and manifestations of toxemia is tuberculosis, a disease as common in the tropics as elsewhere. Then too, one must always keep in mind febrile manifestations not unrarely marking syphilis. This triad of diseases, malaria, tuberculosis and syphilis, must always be thought of, as well as septic conditions, when fever is present in a disease typically afebrile.
There are certain exceptions in the above list which may be here noted.
Beriberi.—There has been considerable discussion as to whether a disease with fever and a rash, but otherwise resembling wet beriberi, is the same disease or a distinct disease entity. The fever in epidemic dropsy; as it is called, is rarely over 102°F., usually ranging from 99° to 101° and accompanying the dropsy.
Pellagra.—While there may be slight variations from the normal yet the ordinary case of pellagra fails to show a distinct febrile course, so much so that the appearance of fever in a case of pellagra makes for an unfavorable prognosis. In the so-called typhoid pellagra, an acute, rapidly fatal form of the disease, a high temperature curve may be obtained. At the same time this condition has been noted by Italian and German writers as being present in patients not showing any rise in temperature. It is possible that the development of enteric fever in a pellagrin may at times be the explanation of the fever.
Cholera.—Instead of a favorable stage of reaction there may set in a condition with low muttering delirium, dry brown tongue and with an elevated temperature, the so-called typhoid state, which is speedily fatal.