_Of the Relation between the Phenomena of Fever; or the Theory of the
Disease._
In the preceding chapters it has been shown what are the real events
which take place in fever, the assemblage of which constitutes the
disease: it has also been shown in what order these events succeed each
other, and upon what conditions of what organs they depend. To assign
further the true relation between these events, is to establish the
theory of fever in the only philosophical sense of the term theory: and
that relation must already have suggested itself to the mind of the
attentive reader.
We have seen that the first indications of disease are clearly traceable
to the nervous system: that the disorder of the functions of the brain
and spinal cord with which the attack always commences, demonstrates
that these organs form the primary seats of the malady: that the
derangement in the functions of these organs is truly _invariable_, and
is invariably the first morbid condition that is observed to take place:
that there never was a case of fever, from the slightest to the most
severe, in which these organs were not in a greater or less degree in a
disordered state, and in which that disordered state did not precede
every other. This affection of the nervous system then, the invariable
antecedent of all that follows, is the primary essential event in the
morbid series which constitutes fever.
What the real nature of this primary affection of the nervous system is,
we are wholly ignorant, and we ought at once to confess our ignorance.
We have already entered into some considerations, derived from the
difference in the order in which the phenomena of fever and of
inflammation succeed each other, to show that these two diseases are not
identical.[30] When these phenomena are still more attentively
considered, other differences are observable between them, which confirm
the opinion that the two diseases are not the same. Not only is
derangement in the nervous and the sensorial functions invariably the
first in the series of morbid events in fever, while it is not the first
in inflammation, but that derangement is always much greater in the
former than in the latter, and proceeds in a regular and determinate
course, such as has been fully explained in the preceding pages, and to
which there is nothing analogous in the progress of inflammation.
To the condition of inflammation a peculiar but an unknown condition of
the blood-vessels appears to be indispensable. To the state of fever, no
such condition of any part of the vascular system, as far as we have the
means of judging, is absolutely indispensable, although it be very
commonly coincident. No such condition appears to be present, at least
no such condition has yet been ascertained to be present, either in the
very mildest or in the severest form of the disease: at the latter
extreme of the scale, at least, we might expect to find the most
striking and unequivocal indications of the existence and operation of
inflammation, were that agent really present; and yet it is precisely
here that the ordinary signs of inflammatory action are completely
absent.
Moreover, we have no example of instantaneous death by the sudden
excitement of inflammation in any organ, or in any number of organs:
inflammation is a process: a certain number of events take place in a
certain order; and there is always, as far as has been hitherto
observed, some interval between these events. A case is recorded in
which inflammation of the bowels (acute enteritis) proved fatal, as was
supposed, in eight hours from the commencement of the attack; but so
rapid was the process, that the intelligent surgeons who witnessed it
doubted whether the time when the disease began could have been noted
accurately: at all events, it does not accord with the best-established
facts relative to the process of inflammation, that it should prove
fatal without the lapse of some hours. Fever, on the contrary, does not
need as much as a single hour to complete the work of death. It is well
known that the poison which, in a certain state of concentration,
produces fever with the ordinary period of duration, in a higher state
of concentration produces instantaneous death; and that, in certain
climates and seasons, it is not uncommon for persons previously in sound
and vigorous health, on exposure to that poison, to sicken and to die in
a shorter space of time than is requisite, under ordinary circumstances,
for the mere formation of the inflammatory process. The state of the
system, in the primary attack of fever, and the state of the system in
inflammation, do not, therefore, appear to be identical. The truth is,
that we do not know what the real state of the system is in either case,
but we see that the phenomena of the one differ from those of the other;
to conclude, therefore, that the states are the same is not a sound
induction. While, then, we are constrained to admit that we know nothing
of the nature of the primary affection of the nervous system in fever,
the closest consideration of all the phenomena alike constrains us to
conclude, that that affection is peculiar and specific.
This peculiar and specific affection appears to be much more analogous
to the condition into which the nervous system is brought by the
application of certain poisons, than to that which is proper to pure
inflammation. The more closely and extensively the subject is
investigated, the more clear and satisfactory the evidence becomes, that
the great primary cause of fever is a poison, the operation of which,
like that of some other poisons, the nature of which is better
understood, and the action of which has been more completely examined,
is ascertained to be upon the nervous system. How these poisons act upon
the nervous system we do not know, nor can we possibly know, as long as
we remain so profoundly ignorant of the nature of the action of the
nervous system in the state of health.
It may be considered then as established, that the primary morbid
condition of the body, in fever, consists of an affection of the nervous
system, which there is reason to believe is of a peculiar and specific
nature, although that nature be at present wholly unknown.
This specific derangement of the nervous system having continued for
some time, the vascular system becomes disturbed. How the nervous system
so influences the vascular as to bring it into the morbid condition into
which it passes, is as unknown to us as the peculiar affection of the
nervous system itself. That there is the most close and intimate
connexion between these two systems, and that they exert over each other
the most important influence both in the state of health and of disease,
are in the present state of our knowledge ultimate facts.
With two apparent exceptions, (whether these two cases form real
exceptions may still admit of doubt) the vascular derangement connected
with, and dependant upon nervous derangement, passes sooner or later
into true inflammation. Of this we have the most complete and
indubitable evidence—evidence derived both from changes, the known
results of inflammatory action, produced in the structure of organs; and
from the generation of new products, such as are formed by no other
known process but that of inflammation. Almost every change of organic
structure which inflammation is ascertained to be capable of producing,
is found to take place in fever: almost every product which inflammation
is ascertained to be capable of forming, is observed to be generated in
fever: it is not possible to doubt, therefore, that the morbid condition
into which the vascular system is brought in the progress of fever, is
that of inflammation. In what circle of organs inflammation is
peculiarly liable to be excited in this disease, by what particular
character febrile inflammation is distinguished, and what remarkable
differences it exhibits in intensity and extent, have been fully
illustrated.
It follows, then, that the second event that takes place in the morbid
series constituting fever, is inflammation.
But however really and constantly inflammation may take place in fever,
and in whatever intensity, and to whatever extent it may be carried, yet
the inflammation is never pure or simple: the condition of the inflamed
organs is never the same as that into which they are brought by mere
phlegmasia: there is always inflammation, and _something else_: and if
what we have so much insisted on be true, this must necessarily be the
case, because the state of inflammation succeeds to another, a distinct,
and a pre-existing condition of the system: that something else is the
unknown, but the peculiar and specific affection of the nervous system,
which has already been stated to be the invariable antecedent of
whatever subsequent affection may take place. Thus this affection of the
nervous system is not only the invariable antecedent of every other
condition, but it is omni-present with every other condition, and its
presence is a most powerfully influential presence; it operates at every
instant, in every organ, and every function of the economy, although, as
we have seen, its operation is peculiarly great, and, as far as we can
perceive, specific in certain organs and functions. The combination of
this nervous affection with inflammation, and the influence which this
combination exerts over the inflammatory state, we express by saying
that the inflammatory state in fever is modified: we see that
inflammation is present, but we see that it is not the same as
inflammation in a pure phlegmasia: we see, as has just been stated, that
there is inflammation, and something else superadded; namely, a peculiar
affection of the nervous system, which gives to the febrile inflammation
a peculiar character, or which modifies it in a specific manner.
It has been stated that there appear to be two exceptions to the
universality of the presence of inflammation. Of these exceptions, one
is exemplified in the mildest form of the disease. In every case of
fever, the function of the vascular system is disturbed in a greater or
less degree, as has been fully shown: but the doubt is whether that
disturbance invariably pass into the state of inflammation. Since the
morbid condition of the nervous system, in the mildest case, remains
only for a certain period, and then uniformly gives place to the return
of health, there seems to be no possible means of determining this
question. And even in the second case, where the intensity of the
nervous affection is incompatible with life, and death follows with
extreme rapidity, the real condition of the vascular system appears to
be equally doubtful. In both, that condition may possibly be a
modification of one and the same state, and that state may be identical
with inflammation—inflammation existing in different degrees of
intensity. On the other hand, both may differ essentially from the state
of inflammation. The nervous affection in the first may be too slight to
excite inflammatory action, while in the second it may be so
overwhelming as completely to oppress every function of the economy, and
therefore, instead of exciting, may paralyse the capillary
blood-vessels; and consequently paralysis of the capillary vessels,
instead of intense excitement of them, may possibly be the real
condition of the vascular system, for example, in congestive fever.
But however this may be, the only difficulty in the subject relates to
these two forms of the disease—the very mildest and the very severest.
In all the intermediate cases, the condition of the vascular system is
clear and certain. In all these, there can be no more doubt that that
system is in a state of true inflammation, than there can be that the
capillary vessels of the pleura are in a state of inflammation in
pleuritis. Yet, as we have just stated, in fever the inflammation is
never the same as it is in pleuritis. In fever there is a combination of
a specific affection of the nervous system, with that specific affection
of the vascular system, which constitutes the state of inflammation: in
pleuritis there is the specific affection of the vascular system,
without the specific affection of the nervous; and this combination of
the two affections in fever modifies the nature of febrile inflammation.
This view of the constitution of fever appears to explain in the most
luminous and complete manner every peculiarity of the febrile state: to
reconcile all its apparent anomalies, with which few who have studied
the subject have not been perplexed: to establish the true distinction
between fever and inflammation; and to show why the phenomena exhibited
by these two affections are so essentially different, and why therefore
each requires a different mode of treatment. In this point of view no
theory was ever more eminently practical, or led to a more guarded
practice. Inflammation does not lose its nature by being combined with
that peculiar affection of the nervous system which converts it into
fever; it only modifies its state: the remedies proper for fever do not
differ from those which are effectual in inflammation; they only require
to be modified in accordance with the modified nature of the disease. He
who believes fever to consist of an affection of the nervous system
alone, every other affection that may be combined with it being
accidental, will rarely think of using the lancet: he who believes fever
to consist of inflammation alone, and overlooks the presence of the
nervous affection, will be apt to carry the employment of the lancet too
far: he alone who embraces the view of both, brings within his own all
the phenomena: he alone adopts a sound theory of the disease, and we now
see that he alone is likely to be led to a sound practice. When the
theory of a disease collects, arranges and points out the true relation
between all its phenomena, there is good reason to conclude that that
theory is sound; but when it moreover directly leads to that treatment
of the malady which experience shows to be the most safe and the most
effectual, its truth is established by every test that can be applied to
it.
The consideration of the diseased states of the other systems and
functions that take place in fever, need not detain us long. The
respiratory appears to be the next function that becomes deranged. The
intimate and inseparable connexion which physiology teaches us subsists
between the respiratory and the circulating systems, might lead us to
anticipate the fact which pathology demonstrates. We know that the
respiratory system is constructed for the circulating: that the form,
the extent, the complication of the respiratory apparatus depend
entirely upon the quantity of blood that is to be regenerated, and the
degree of perfection with which that regeneration is to be accomplished.
It is therefore impossible that any considerable derangement in the
function of one of these systems should continue long, without being
accompanied with a proportionate derangement in the other. The function
of respiration cannot be materially deranged, without producing a morbid
condition of the blood, that vital fluid which it is the specific object
of the process to purify and regenerate. The function of secretion
depends upon the quality of the blood conveyed to the secreting organ,
upon the action of the capillary vessels of that organ, and upon the
supply of nervous influence received by those vessels; it follows, that
in a disordered state of the nervous, the circulating and the
respiratory organs must be attended with a derangement in the process of
secretion; while the excreting being necessarily connected with the
secreting processes, the vitiation of the one cannot fail to occasion a
corresponding deterioration of the other.
Thus we see that the organs and functions deranged in fever are closely
and inseparably connected: that no continued disorder can take place in
the one, without producing a proportionate disorder in all the others:
that a peculiar and specific affection of the first, according to the
established laws of the vital economy, invariably produces a peculiar
and specific affection of the second, and the second, a third, and so on
throughout the circle. And now we see why a certain number of organs are
invariably affected in fever; why these organs invariably become
affected in a certain order; why the nature of their affection is
invariably the same; and why, finally, the ultimate condition of the
system, the general result of these individual morbid changes, never
varies.
Writers on fever in general have confined their account of the phenomena
of this disease to an explanation of the relation between the cold and
the hot fits. Were their success in establishing that relation as
complete as it is defective, they would still have done little or
nothing, by a view so incomprehensive, towards establishing the theory
of fever. Both the cold and the hot fits, about the exposition of which
such a theory is alone concerned, are themselves accidents, since in the
most formidable and dangerous forms of fever, the supposed relation
between these phenomena is not only constantly disturbed, but often the
phenomena themselves do not occur, it being one of the very characters
of some of the intensest fevers, that the temperature is little changed,
and that the diminished temperature which may be, or which may have been
present, is never succeeded by any increase of heat. The true theory of
this, as of every other disease, must be sought in the study of its
pathology, and can be found only by comparing the pathology of the
organs ascertained to be affected with their physiology. The cold stage
of fever, when it exists, is produced by a disturbance of the functions
of the circulation and of the respiration, and these functions are
disturbed, because the organs in which they have their seat no longer
receive their accustomed and their requisite supply of nervous influence
from the nervous system. The hot stage, when it exists, arises from a
disturbance of the same functions: and the reason why we cannot assign
with precision why the same cause produces in the one case a diminished,
and in the other an increased temperature, or why the temperature is
disturbed at all, is because we do not know with precision on what
circumstances in the animal economy the generation of heat depends: when
the physiologist has clearly and completely ascertained all the
circumstances upon which this process depends, the pathologist will
probably have but little difficulty in tracing with equal clearness and
completeness the connexion between the disturbance of that process, and
the commencement of the febrile state.
In conclusion, then, the doctrine of fever which appears to approximate
most nearly to the truth, may be summed up in few words. The immediate
cause of fever is a poison, which operates primarily and specifically
upon the brain and the spinal cord. The diseased state into which these
organs are brought by the operation of this poison, deprives them of the
power of communicating to the system that supply of stimulus (nervous
and sensorial influence) which is requisite to maintain the functions of
the economy in the state of health. The organs, the seats of the
functions, deprived of their supply of nervous influence, become
deranged, the derangement in each taking place in a fixed order, and in
a determinate manner. Subsequently to the nervous and the sensorial, the
organs the next to suffer are those of the circulation; then those of
respiration; and, ultimately, those which belong to secretion and
excretion. The condition of the nervous system which produces this
derangement in this circle of organs, occasions further, in that portion
of the circulating system which consists of the capillary blood-vessels,
that peculiar state which constitutes inflammation: hence inflammation
is almost always established in one or more of the organs comprehended
in the febrile circle, and sometimes in all of them. The peculiar and
primary affection of the nervous system, which is here assigned as the
cause of inflammation, does not become identical with inflammation, but
superadds the morbid condition of inflammation to its own; does not
lapse into or terminate in the inflammatory state, but accompanies it,
and by this combination modifies in a peculiar manner the inflammatory
process.
The great practical conclusion to be deduced from this doctrine of fever
is, that while the inflammatory processes that are thus set up in so
many important organs, greatly aggravate the severity of the disease,
and ought to be constantly kept in the view of the practitioner, both on
account of their own peculiar danger, and also because they are perhaps
the only real states over which he has any control, yet that these
inflammatory processes do not alone constitute fever; that their
removal, though essential to the cure, will not complete the cure; that
another, a primary, and a most formidable disease, is at the same time
to be contended with, and that the presence of this distinct and primary
disease requires very important modifications in the treatment of the
inflammatory condition.