Means of diagnosis. Usual health of the subject. History of the
attack. Objective symptoms, interdependent disease, fever, diseases
that may be confounded, subsidiary disease, diagnostic signs, organ
involved, pathological test injections, course of disease, sporadic or
zymotic, result of treatment.
Diagnosis is the determination of the seat and nature of a given disease
and its distinction from other morbid conditions. Its importance to the
practitioner cannot be overestimated as it occupies the pivotal position
between causes, nature, morbid phenomena, and symptoms on the one hand,
and prognosis, prevention, and treatment on the other. Unless the
conclusions are sound as to causes, nature, lesions, and symptoms, there
can be no certain diagnosis, and without a correct diagnosis, prognosis,
prevention, and treatment can have no intelligent or scientific basis.
The practitioner who finds a dropsical condition and who is satisfied to
pronounce it dropsy and institute treatment is abusing his trust. He
must find whether this dropsy results from disease of the kidneys,
heart, bloodvessels, lymphatics, liver, lungs, bowels, or the structures
in which it is shown; whether it is due to parasites or imperfect
sanguification or to other morbid conditions, before he dare prescribe
treatment and predict results. So in every other affection; the failure
to make a correct diagnosis opens to the practitioner many doors of
error, and he is happy indeed if he can escape the injuring of his
patient.
In seeking a sound diagnosis we must attend to the following among other
indications:
1st. The habitual state of health of the subject. The genus, breed, age,
environment, habits, (pet dog, watch dog, hound, sheep-dog, ox, bull,
cow, milch cow, sheep in the field or housed, pig in pen or at large,
diet, regimen, water, race horse, draught horse, work, exposure, etc.)
as well as the personal equation of temperament, idiosyncrasy, heredity,
etc., must all be carefully considered.
2d. The history of the present illness as to its apparent cause, mode of
invasion, duration and progress.
3d. The objective symptoms by which it is manifested. All that can be
ascertained in the way of symptomatology, local and general, the
probable existence of interdependent disease, and all actual structural
lesions and disorders of function should be thoroughly investigated. As
supplementary to the more prominent objective symptoms any fever or
other constitutional disorder must be sought for; a mental list must be
made of the diseases which resemble this one, and these must be excluded
one by one by careful attention to the differential symptoms; other
diseases which are probably subsidiary to this, should be similarly
investigated and excluded; any really diagnostic sign of the suspected
disease must be carefully established and the diagnosis finally placed
on a solid foundation. The discovery of a constitutional (febrile)
disease to which a distinctive name can be given is by no means the end
of the diagnosis; the structural lesions of the disease may be largely
localized in an unimportant organ where they may remain circumscribed
without compromising life, or they may be seated in a vital organ which
will render the disease grave to the last degree or necessarily fatal.
For example: Anthrax of a dense, dry part of the skin may be a mild
local disease; anthrax of an internal organ is usually fatal. Every
local complication therefore, should be as carefully diagnosed as the
connected constitutional disorder.
But diagnosis cannot always be certain. In the early stages of certain
fevers two forms may be as yet indistinguishable and a day or two may be
required to develop differential symptoms. In some occult forms of
disease all differential symptoms may fail us. A method of diagnosis
which has hitherto been applied only to tuberculosis and glanders is
manifestly capable of much wider application, to diseases attended with
a febrile reaction. This consists in a hypodermic injection of a minimum
dose of the sterilized and filtered products of the culture of the
disease germ, which produces no effect on the healthy system but causes
febrile reaction or local inflammation, or both, in the diseased. This
will be treated more fully under the respective diseases.
In connection with such a method, but above all when no such resort has
been had, the obscure case should be seen frequently, the course,
duration, and termination of the disease should be noted, also its
tendency—sporadic or epizootic, and finally the result of treatment.
This last resort may often secure diagnosis and cure at once as when a
course of iodine cures an obscure actinomycosis.