Vol. 60, 1909 - University of North Carolina at Chapel Hill

74
THE CHARLOTTE MEDICAL JOURNAL.
shown to produce disease in man,—in the certain diseases were not apt to have them
lower animals the number of pathogenic again, at least not within a comparatively
forms is slightly larger,—but the study of short time. But the reasons for this immunthese
micro-organisms offers an interesting ity, natural or acquired, are still but parfield
for further investigation,
tially known.
Pathogenic micro-organisms may be con- Whenever the power of resistance is lost
sidered to cause disease either by their me- or diminished, however,—and anything
chanical presence in the tissues, by the poi- which lowers the general or local vitality of
sons produced by tkeir growth, by the with- the tissues, such as hunger or poor food,
drawal from the body of necessary food bad hygienic surroundings, exhaustion from
substances, or possibly by other ways as yet over-exertion, mental depression, exposure
unknown. Although injury is probably to cold, the deleterious effects of poisons,
caused by all these different means, it is bacterial or chemical, acute and chronic
now believed to be chiefly due to the reac- diseases, vicious habits, drunkenness and
tion upon the body cells of the poisons excesses of all kinds, etc., reduces the
elaborated from the tissues by the germs in power of resistance,—whenever this power
their growth. Each variety of germ proba- is lost or diminished, we run a grave risk of
bly produces one or more specific as well as contracting disease.
general poisons, some of which have been i It may be well to state here in parenthepartially
isolated and studied, as in tetanus sis, that in discussing the theories of imand
diphtheria. Bacteria cannot grow and munity and infection it should be rememmultipiy
either in the living body nor out- bered that, however interesting or plausible
side of it without proper nourishment and they may be, they are only theories and
suitable conditions, such as adeciuate mois- may be shown to be untrue. )
ture, light, temperature and air; nor can But granted that somehow or other the
they develop without changing the sub- micro-organisms have gained entrance into
stances upon which they grow. Outside the body and that infection has taken place,
the body this activity gives rise to the pro- let us endeavor to trace briefly and clearly
cesses of fermentation, putrefaction, etc., what is thought to occur. Between the
inside the body to disease. time when the bacteria effect a lodgment
There are many complex factors influenc- and that in which the disease manifests iting
the susceptibility of the body to infec- self the patient simply is troubled with mation
from any germ, only a few of which laise, he feels languid and out of sorts.
are as yet completely understood. The This is the stage of incubation, and it is
most important, however, and perhaps the during this stage that the blood and tissues
all-embracing, one is the condition of the are deeply engaged in the effort to repel the
body at the time of infection, whether it is attacks of the invading germs. These niulfavorable
or unfavorable for the growth of tiply, however, with varying speed throughthe
organism,—whether the soil is suitable out the body generally, or they may be at
or not for the development of the seed. For first localized, or even remain localized, as
without the existence of proper conditions in tetanus, all through the disease. Growno
germ can produce disease. In the living ing in the tissues, they generate in increasbody
the conditions are naturally unfavor- ing amounts their poisons or toxins, which
able for the growth of bacteria, even after soon cause profound changes in the body;
they have penetrated the epithelial invest- the patient becomes really ill and shows
ments of the skin and mucous membranes, signs of unmistakable infection,
wliich so long as they remain intact protect What then happens? Does the body give
the interior from bacterial invasion. Xor- up the fight entirely? No indeed; the white
mal blood has of itself, to a considerable blood cells, the wandering cells and the
extent, a bactericidal power; and the tissue cells of the tissues most affected still keep
cells of the body in general show a similar up an unequal combat. From the lymaction,
depending upon the different cell phatic glands and spleen, armed hosts of
groups, state of health, robustness, and white blood cells rush to the front and atperiod
of life of the individual attacked, tempt to destroy the foe, but all in vain.
This resistance to or protection against in- perhaps; the disease runs its course, to end
fection varies in different Individ- either in death or recovery. But if the case
uals toward the same bacteria, and in terminates in recovery, how are the microdifferent
degrees in the same individual organism finally overcome? This question
toward different bacteria,—which resistance involves many complicated processes, which
may be either natural or acquired. Long time will not permit us to go into in detail,
before bacteria were discovered a difference but the main principles are as follows;
in individual susceptibility, or refractoriness As has been previouslv noted, once the
to different diseases, was recognized. It was bacteria obtain a firm foothold in the body
also noticed that persons who contracted it is subjected to the action of generated