Watery liquors, which increase the fluidity of the blood, and render
several of the secreted and excreted fluids less viscid.
There are certainly few remedies whose operation is more simple,
obvious, or important; and yet there are scarcely any whose value has
been more mistaken, or whose application has been so frequently
perverted through the suggestions of false theory; water is the
universal beverage of animals, and the necessity of its supply is
indicated by thirst, a sensation which in excess, is borne with less
tranquillity even than that of hunger; in certain morbid states of the
body its presence is to be regarded as indicating the necessity of
copious potation; and yet how often has the prejudiced physician, under
such circumstances, aggravated the pressure of disease, by adding the
sufferings of Tantalus. In febrile affections, the irritation of thirst
tends to keep up the disease, and hence diluents, besides the other
beneficial effects which they may produce, must be regarded as important
remedies. There are also diseases of the alimentary canal which may be
removed by the same agents; when water is conveyed into the intestines
it will have a tendency, by mixing with, and diluting the biliary
secretion, to diminish its acrimony, and thus to obviate a source of
morbid irritation; the dilution of the chyme and chyle may also have a
salutary tendency, and favour the absorption of the finer and more
nutritive parts of the lacteals; and by increasing the fluidity of the
mass, expedite the numerous combinations which it is destined to
undergo. The blood itself is also thus modified in its fluidity;
although it has been very truly observed that in healthy bodies, or such
as are without any obstruction of the excretions, an unusual distension
of the vessels cannot be produced, or at least long subsist; for it is
evident that such an increased quantity of water in the blood will
immediately pass off by one or other of the excretions; this effect,
however, in itself, renders the operation of diluents of signal service
in the treatment of the disease; in consequence, for instance, of their
disposition to pass off by urine, they furnish valuable resources in
diseases of the urinary organs, allaying the pain of strangury, and the
irritation from an inflamed bladder. From these observations, the
practitioner will be led to appreciate the value of diluents; and many
of the beneficial effects which are daily experienced from the copious
potation of mineral waters, are, without doubt, to be wholly attributed
to simple dilution. See _Aqua_.
It is here necessary to say a few words upon the misapplication of this
order of remedies. Dr. Davy found by experiment that when an animal is
bled to death, the last portions of blood that flow are of a much lower
specific gravity than that which flows first, in consequence of the
former containing more water, which it may be inferred was derived by
the increased activity of the absorbents, exerted chiefly on mucous and
serous membranes. Since then venesection promotes and accelerates
absorption,[236] it is clear that, in inflammatory diseases, where we
have recourse to blood-letting, in order to diminish the volume of
circulating fluids, we ought not to suffer the patient to indulge in an
unrestrained use of liquids, which he eagerly demands to satisfy a
thirst which, in all probability, is the natural consequence of
increased absorption. In such cases, it is often better to take liquids
in small divided doses, which will have the effect of moderating the
thirst, without overloading the arterial system, and bringing on that
tension and plenitude which are liable to be produced by swallowing too
large a proportion of liquids.
In the use of water upon such occasions, it may moreover be observed,
that its temperature ought to be attended to; as a general rule it may
be laid down, that in the _cold_ stage it should be hot, in the _hot_,
cold, and in the _sweating_, tepid.
With regard to the value of diluents, as capable of promoting the
operation of other remedies, many observations of great practical
importance might be adduced; but this subject will be more properly
elucidated when we come to consider the influence of solubility in
modifying the activity of medicinal substances, and which constitutes a
very curious and interesting object of chemico-medical enquiry.
While speaking of Diluents it may be cursorily noticed, that water
appears, under certain circumstances of the body, to suffer
decomposition, and to have its elements appropriated to new
combinations. Count Rumford has endeavoured to prove, that the
surprisingly small quantity of solid food which is sufficient for
nourishment, when converted into rich and palatable soup, is owing to
the culinary process having prepared the water for chemical
decomposition,[237] and that this is ultimately effected during the act
of Digestion.[238] It cannot be denied that the exorbitant potation of
water has a tendency to produce fat, but this may depend upon the
vascular distention which is thus occasioned. Gin drinkers, before they
become materially injured by the habit, grow extremely corpulent, as may
often be witnessed in unfortunate cyprians of the lower orders. Can the
hydrogen of the spirit contribute to this effect?