It would appear that the action of the vessels employed in the
circulation of the blood, and the energy of the absorbents are, to a
certain extent, antagonist powers; the experiments of Majendie
demonstrate that the absorption of a poisonous substance is retarded by
a plethoric, and accelerated by a depleted state of the sanguineous
system; the fact is practically established by numerous phenomena in
pathology. Dr. Blackall has very satisfactorily shewn the existence
which subsists between increased arterial action and diminished
absorption. Hence it follows that remedies capable of controlling the
circulation may affect the activity of absorption, increase diuresis,
and cure dropsy; in this manner the _Digitalis Purpurea_ acts as a
sorbefacient, and it may be remarked that it seldom or never produces
its diuretic effects, without a concomitant reduction of the frequency
of the pulse; its power too appears only when it is administered in
dropsy; in a state of health it will reduce the pulse, but not increase
the discharge of urine. Tobacco has also somewhat analogous powers in
promoting absorption, and its operation is accompanied with a
corresponding depression of vascular action. Venesection, upon the same
principle, may occasion, in certain cases of dropsy, a discharge of the
accumulated fluid.
2. _By increasing the tone of the Body in general, and that of the
Absorbent System in particular._
That diminished absorption, and the consequent accumulation of serous
fluids in the cellular texture, and different cavities, frequently
depends upon general debility is very obvious, whence fevers, whether of
the intermittent, or continued kind, which have been long protracted,
are followed by _œdematous_ swellings. In states of extreme debility the
exhalant vessels would seem, from their laxity, to permit the thinner
parts of the blood to pass too readily through them; this is proved by
the circumstance that palsied limbs, in which such a laxity may be
presumed to exist, are frequently affected with _œdema_, and the truth
of this explanation is still farther corroborated by the advantages
which accrue on these occasions from the mechanical support of pressure
from bandages. In such cases, those remedies which are capable of
renovating the vigour of the body can alone prove of any signal service.
Dr. Blackall presents us with an illustrative case of this nature, on
the authority of Mr. Johnson of Exeter, in which the tonic powers of
well fermented bread occasioned in the space of a few hours an effect so
powerfully diuretic, as to have cured sailors on board of the Asia East
Indiaman, who had been attacked with Dropsy, in consequence of the use
of damaged Rice.
Thus then do Diuretics, in some cases, CURE BY EVACUATING, while in
others, as in the instance above cited, they EVACUATE BY CURING.
A case has lately occurred in my own practice, which not only affords a
striking illustration of the present views, but is well calculated to
convey to the inexperienced practitioner a very instructive lesson of
caution. A man of the age of thirty-five, of the most dissolute habits,
was attacked after a debauch of several days’ continuance, with
inflammatory symptoms in the chest; a very large quantity of blood was
suddenly abstracted, and the bleeding was repeated after the interval of
a few hours. The respiration became laborious, and I was desired to
visit the patient; I found that little or no urine had been evacuated
since the attack, and that there were evident symptoms of effusion, the
legs were swollen, and the difficulty of breathing was rapidly
increasing. Under these circumstances I directed a large dose of
_Ammonia_ with some stimulating diuretics, which were to be repeated at
short intervals. On the following day the distressing symptoms had
subsided, a large quantity of urine had passed, and the patient
expressed himself greatly relieved; unfortunately, however, in
consequence of a slight increase of his distress in the evening, an
injudicious friend in attendance, took more blood from the arm—the
dropsical effusions rapidly increased, and life was extinguished in the
course of three days by confirmed Hydrothorax.
3. _By producing Catharsis, and thereby increasing the action of the
Exhalants_ directly, _and that of the absorbents_ indirectly.
It has been already stated, under the consideration of Cathartics, that
certain medicines of that class excite the exhalants of the alimentary
canal, and occasion a very copious discharge of serous matter: by this
operation the blood is deprived of a large portion of water, and the
absorbents are thus indirectly stimulated to supply the deficiency;
_Elaterium_, and some other _hydragogue_ cathartics, may be thus
employed with extraordinary success for the cure of certain forms of
Dropsy, where the vital powers of the patient can sustain the violence
of the remedy;—in the whole circle of medicinal operations there is
nothing more wonderful than this, that an impression made on the
internal surface of the _primæ viæ_, by a few particles of matter,
should thus convey by magic as it were, an impulse to the most remote
extremities, rousing their absorbents to action; and, in case of _œdema_
there, awakening the sleeping energies of these vessels, which like
millions of pumps at work, transmit the morbid fluid to the intestines
and urinary passages, effecting a detumescence of the hydropic limbs in
the course of a few hours, and thus affording a striking illustration of
the sympathetic action of medicines, and an instructive example of the
operation of those of the sorbefacient class.[160]
The observations which I have thus offered will lead the practitioner to
select the particular diuretic which is best calculated to fulfil the
indications of each individual case; and they will at the same time
point out those which cannot be administered in combination, without a
violation of the law of medicinal compatibility. With respect to the
general efficacy of these medicines it may be stated, that where the
disease originates from _organic_ affections of the chylo-poietic
viscera, it will not be cured by the mere evacuation of the water by
diuretics; but that where it has taken place from diminished absorption,
these remedies may be reasonably expected to effect a cure.