PHYSIOLOGICAL PROPERTIES.
Prejudice is the daughter of ignorance; and nothing exemplifies the
truth of this more thoroughly than the senseless repugnance to salt
which is now so remarkably prevalent. Ask these persons for their
reasons, if we can dignify them as such, for disliking salt; their
answers, as a rule, will be trifling platitudes, altogether unworthy of
refutation, or even of moderate attention.
Objections founded on imperfect, or an affectation of knowledge, are
not worth the trouble of confuting, even if they be supported by a
fair amount of intelligence; but when the opponents of salt begin to
base their assertions upon science, and demur on medicinal, dietetic,
and physiological grounds, then we must meet them armed with similar
weapons to those they have chosen, with the handling of which they are
but imperfectly acquainted, and which therefore recoil upon them in
such a way as prove that though they may be shrewd, they are but badly
informed and credulous scientists.
At the present day the science of physiology has arrived at such a
pitch of perfection that there is not a single secretion, tissue, or
organ of the body, with the exception of the spleen, which has not been
investigated, and the functions divulged and made so plain that it is
quite divested of that apparent mystery which formerly enshrouded it;
though our kind friends, the anti-vivisectionists, would willingly
adopt the most unjust measures to prevent the study of life from
being more perfect than it already is: they protest with well-feigned
horror at a frog or a rabbit, under the influence of chloroform, being
experimented upon for the benefit of humanity, while they see, without
allowing a sign of disapprobation to escape from them, an inoffensive
hare chased to death for the amusement of gentility, and probably
gloat over, with pleasure, the dying agonies of a stag: a sight which
gratifies the somewhat questionable proclivities of refined and elegant
ladies, who race their horses out of breath to gaze on the sanguinary
scene.
Had it not been for physiological research we should not have known
that the chloride of sodium was such an important constituent in the
animal economy; we should have been in utter ignorance of the science
of life, and we should never have known how man is begotten, how
developed, or how he dies. With regard to the two processes of decay
and repair, or how the human organism, from a mere cell, gradually
becomes a being highly organised, mentally as well as physically, we
should have known nothing. Physiology has been a boon to humanity and
an inexhaustible field of research to the scientific.
In a chemical point of view there is no more important mineral
constituent in the human body than the chloride of sodium, for it
occurs nearly in every part of the system, both solid and fluid,
in close and intimate relation with the organic compounds, and it
materially influences their chemical and physical properties; for
instance, the albumen partly owes its solubility to the presence of
salt, the quantity of which causes the differences which it presents
as regards its coagulation; pure caseine, which is quite insoluble,
is dissolved at once on the addition of common salt; and if it is
added in increased proportions it impedes the coagulation of the
fibrine. Another remarkable physiological fact is that the chloride of
sodium is not only uniformly present, but its various proportions are
nearly definite and constant, both in the fluids and tissues; and the
existence of a provision for the limitation of the quantity kept in
the system causes the proportions to be little affected, in the way of
excess at least, by the amount of salt the food may contain, that is,
if the diet is wholesome and the individual healthy.
According to Lehmann, who experimentalised on himself, the blood may
contain in a normal state 4·14 parts of the chloride of sodium in
1000, and after a meal of very salty food it may be only increased to
4·15; he says it only rose to 4·18 when two ounces of salt had been
taken an hour before, and two quarts of water had been drunk in the
interval. The blood will not receive more than a certain amount; and
as an over-amount of salt will produce extreme thirst, a quantity
passes through the kidneys with the water that has been drunk; frequent
drinking of course causes frequent micturition. If we take the mean
of numerous observations by several experimenters, the average
quantity of urine voided by healthy adult males is about 52-1/2 fluid
ounces; this quantity may contain urea to the amount of 512·4 grains,
chlorine 105·0 grains, and soda 125·? grains, besides other salts and
extractives. If such an amount passes out with the urine we can easily
account for the slight increase in the blood of Lehmann.
The quantity of the chloride of sodium in the blood is liable to great
variation in different diseases; and there can be little doubt that
this variation is closely connected (though whether in the relation of
cause or in that of effect, we are not exactly entitled to surmise)
with the histological and other transformations of the component
parts of the blood. The proportions of salt greatly differ in several
tissues, and also at different periods of the development of the same
tissue. “Thus in muscle,” according to Enderlin, “100 parts of the ash
left after incineration of ox-flesh yielded nearly 46 per cent. of the
chloride of sodium and potassium; which, as this ash constitutes 4·23
per cent. of the dried flesh, would give 1·94 as the proportion of the
chloride of sodium in 100 parts of the latter; and reckoning this dried
residue to constitute 28 per cent. of the whole substance of the muscle
(the remaining 77 parts being water) the proportion of chloride of
sodium in the latter will be 0·44. These figures, as will be presently
seen, bear a remarkably close correspondence to those which represent
the proportion of chloride of sodium in the ash, solid residue and
entire mass of the blood.”[57]
Next to muscle, cartilage contains the largest amount of the chloride
of sodium, and this especially in the temporary cartilages of the
fœtus, its place being taken by the phosphate of lime as it approaches
the time of birth. The percentage of the chloride of sodium contained
in the ash of the costal cartilage of an adult is about 8·2; in the
laryngeal cartilage 11·2; but as the ash does not constitute above
3·4 per cent. of the entire substance the percentage of the chloride
of sodium in the latter is, at the most, 0·38 of the whole, or less
than that of blood and muscle. Only from 0·7 to 1·5 per cent. could be
extracted from the ash of bone.
Besides the important uses of the chloride of sodium in the blood to
which we have already adverted, it serves the purpose of furnishing the
hydrochloric acid required (by many animals, at least) for the gastric
secretion; and it likewise supplies the soda-base for the alkaline
phosphate, whose presence in the blood appears to serve a most
important purpose in the respiratory process. Moreover, there is reason
to think, from the experiments of Boussingault upon animals, as well
as from other considerations, that the presence of salt in the blood
and excreted fluids facilitates the deportation of excrementitious
substances from the blood. The proportion in which it occurs in
the principal animal fluids is represented by the following table,
constructed by Lehmann chiefly from his own analyses; it is highly
interesting, and shows us at a glance that it is more important in the
economy than any other substance, and is significant of the fact that
health cannot exist long if the chloride of sodium is below the normal
amount.
PERCENTAGE OF CHLORIDE OF SODIUM IN VARIOUS ANIMAL FLUIDS, THEIR
SOLID RESIDUE AND THEIR ASH.
Liquid. Solid Residue. Ash.
Human Blood 0·421 1·931 57·641
Blood of Horse 0·510 2·750 67·105
Chyle 0·531 8·313 67·884
Lymph (Nasse) 0·412 8·246 72·902
Serum of Blood (Nasse) 0·405 5·200 59·090
Blood of the Cat (Nasse) 0·537 2·826 67·128
Chyle (Nasse) 0·710 7·529 62·286
Human Milk 0·087 0·726 33·089
Saliva 0·153 12·988 62·195
Gastric Juice of Dog 0·126 12·753 42·089
Human Bile 0·364 3·353 30·464
Mucus (Nasse) 0·583 13·100 70·000
Serum of Pus (Nasse) 1·260 11·454 72·330
We have thus proved physiologically that the chloride of sodium holds
a most prominent position among the other constituents of the body;
that it is present in considerable quantities in muscle as well as in
the blood; and that it furnishes the acid, which is necessary for the
stomach to perform its functions of digestion. It holds the albumen
partly in solution, and its coagulation is dependent more or less on
the amount of salt which is present in the blood, and it also possesses
the power of preventing the coagulation of the fibrine. In fevers the
blood is generally thicker, and has a tendency to coagulate by reason
of the partial absence of salt, because a good deal passes off with the
perspiration; and fever patients always prefer salt to sugar, for while
one refreshes them and helps to restore the usual healthy tone of the
palate, by constringing the papillæ of the tongue, the other raises
feelings of disgust.
It is also present in cartilage, though in a lesser degree than in
blood or muscle, because in cartilage there is no disintegration or
waste of tissue, and therefore it does not require such a perpetual
supply; there is, on the contrary, a continual loss going on in muscle,
especially during exertion. Perspiration is to a certain extent the
principal medium which carries off the chloride of sodium, owing to
its being held in solution by the liquor-sanguinis; during fatigue,
particularly if prolonged, a greater quantity passes off, producing
various degrees of thirst. That the normal proportion of the chloride
of sodium should be regularly maintained must be obvious.
In febrile disease the fibrine of the blood is materially increased,
and there is also a marked decrease of salt, which is dependent on a
greater or lesser intensity of the attack, rendering the blood denser,
owing to the fact of the tendency of the fibrine to coagulate by reason
of the diminution of the chloride of sodium, causing the blood to
circulate slowly and with difficulty.
In some other morbid conditions, which we have already noticed,
the blood becomes thinner and poorer; and consequently the system
degenerates, and we get an anæmic, or chlorotic tendency, especially if
there is a scrofulous diathesis. There are other blood diseases, as the
reader may suppose, and which are more truly such, than those to which
I have just alluded, into the phenomena of which it is not necessary to
enter.
In health what a decided difference! the specific gravity of the blood
is uniformly equable;[58] it circulates with comparative ease; and the
whole system is permeated with the life-giving and health-preserving
chloride of sodium, and the coagulation of the fibrine is prevented
by nothing else but that mineral and inorganic substance—salt,
which at the same time purifies and maintains the equalisation of
the constituents of the blood. By it also the hydrochloric acid is
supplied to the stomach, enabling that organ to perform its functions
of digestion in accordance with the laws of health; and it likewise
furnishes the alkaline phosphate “whose presence in the blood appears
to serve the most important purpose in the respiratory process.”
What stronger evidence do we require to prove the salutary efficacy
of salt? No wonder that it is so frequently reverted to in Holy Writ;
neither can it be a source of surprise that it has been so carefully
cherished and extensively utilised from time immemorial. What is to
be regarded as an extraordinary anomaly is that there are not a few
who are entire strangers to its virtues, and who prefer impurity and
defilement to the luxury of health and cleanliness.
Those who desire more conclusive proof of the utility of salt, of its
necessity in the animal economy, and of the peculiar morbid phenomena
to which its absence in the system gives rise, I would refer to two
articles which appeared at different times in the _Medical Press and
Circular_, and in the _Medical Times and Gazette_.[59] The cases I
there mention occurred in different localities, and they demonstrate
incontestably that parasites, especially the _lumbrici_ (the _tæniæ_
are well known to infest adults of impure habit), are sometimes
the origin of strange and incomprehensible symptoms of a deceptive
character, rendering diagnosis extremely difficult and unsatisfactory,
and frequently endangering the lives of the sufferers. Is it not a
blessing to know that nature has munificently provided a means whereby
these distressing evils may be checked and definitely eradicated by
a daily use of such an enemy to, and destroyer of, disease as the
chloride of sodium, universally known as common salt?