Omaha daily bee., 1919-05-04
Phenomena OF Infection.

vEcnOmena OF injection.
There are two viewpoints from
which the production of an infecti-
GUS disease must always be studied,
viz, a., the injecting micro-organ-
ism, and (2), the state of the body
at the time the infection occurs.
Apart from injuries and direct pois-
onings there are no independent
causes OF disease. When We say an
infectious disease is due to this or
that micro-organism,/ we are max
ing statement which expresses only
a fraction of the true sequence of
events, since unassisted, infectious
agents probably never, under ordi-
nary conditions Of life, bring about
disease. To be sure, their presence
in an infectious process is indispen-
sable, yet the mere fact of their pres
ence counts for naught unless the
BODY has been prepared, so to speak,
for their invasion. Furthermore,
even in the event that the body be
in a most favorable condition for
infection, there are several condi-
lions which micro organisms must
fulfill before they can exercise their
specific functions.
For the foregoing reasons, there
fore, an infectious disease is the re-
suit OF the co-existence of chain of
fortuitous phenomena which concern
the body on the one hand, and the
infectious agents on the other. To
illustrate: We say that the germ,
pneumococcus, Is the cause Of pneu-
monia because it is found in the
sputunl in pneumonia during life,
and in the lungs after death. I'm
questionably. it is necessary fac
tor in the disease; but is 1t the sole
factor? We have only to examine
the facts in the case to discover that
1t Is not In the first place, prac-
tically every one, even in health,
harbors the germ of pneumonia in
his mouth. In the second place,
pneumonia in robust individuals in
variably follows either fatigue and
exposure to inclement weather, or
exposure and over-indulgence in in
toxicants; often a combination of all
three factors precedes the onset. In
the less robust, e. g., those suffering
firm chronic ailments-(a condi-
ton in which susceptibility to pneu-
monia is especially marked), it is
the pre-existing sub-normal state of
the health which permits the micro
organisms to invade the deeper air
passages and produce the disease.
Again: 1t is matter of common
observation that Of a number of in
divlduals exposed to the same in
fec -.ous disease not all are attacked,
anC that in those susceptible the dis
ease presents extraordinary varia-
lions as regards it's mildness or Sc
YER. If the microbe were the sole
factor concerned, all exposed 1ndi-
viGuals would be attacked, and all
attacked would suffer. to the same
degree; a thing which everyone
knows never happens. Moreover, a
person may resist the action of a
pathogenic agent at one time and
fall victim to 1t at another.
Infectious Agents in Disease.
From the view point of thes in
fectious agents there are five condi-
lions to be fulfilled before they can
provoke disease:
1) They must be present in suf-
ficient numbers.
(2) They must reach (what is
for them) their portal of entry.
CD They must be virulent.
"a In the case of certain patho-
genie agents, disease can result only
when the agent is accompanied by
one or more other ro-organisms,
or when accompanied by a foreign
body.
CD II the disease is conveyed ex-
| clusively by an insect, a fact in a
certain number of diseases, obvious
| ly the presence of that insect is an
essential condition.
These five conditions will be dis
cussed next week.