EVILS RESULTING FROM INEFFICIENT MASTICATION
_Too much food is eaten._--Inefficient mastication conduces to
excessive eating. Now it is obvious that soft foods, and these
constitute the bulk of our modern dietary, pass much more readily into
the stomach than coarse, hard foods which compel a certain amount of
preliminary mastication, and for this reason the former predispose to
excessive eating: hence a danger at all periods of life, not only in
grown-ups but in children, even infants; brought up as the latter are,
mainly on liquid and pappy foods, many of them consume not only far
more than is needful, but far more than is healthful, their stomachs
being literally deluged with nutriment.
When the food is of a kind necessitating abundant mastication it is
much less likely to be taken in excess, for the longer the time spent
in mastication the less will the individual be tempted to consume;
even in the case of soft food, less will probably be eaten if it be
thoroughly masticated and insalivated than if it be bolted. Thorough
mastication, however, not only tends to diminish the amount of food
consumed on account of the time and labour which it entails; it
actually reduces the amount needful to constitute a sufficiency, for
the more perfectly the food is chewed the more perfectly is it digested
and the more economically is it disposed of in the system; the less,
moreover, is the tendency to that morbid craving for food which is so
frequent an accompaniment of defective digestion. It is certain that
appetite and the needs of the system are sooner satisfied when food is
well masticated and digested than when it is swallowed whole.
_A mass of unmasticated food may lodge in the throat and cause fatal
suffocation._--This may seem to be a very exceptional kind of evil,
but I am informed by one whose experience makes him an authority
on the ways of the British soldier that it is by no means uncommon
for soldiers in barracks to die from this cause. Usually it is when
they are under the influence of alcohol that fatal results occur,
post-mortem examination disclosing large undigested masses of food in
the stomach. A like experience is also frequently met with in the case
of men killed by accident.
_The presence of masses of imperfectly masticated food in the stomach
may cause disturbance either mechanically or by reason of their
imperviousness to the gastric juices._--We have already seen that the
digestibility of a food is largely determined by its consistence, and
that many articles of diet, such as cheese, hard-boiled egg, cocoa-nut,
lobster, and new bread, which have the reputation of being very
indigestible, can, if finely comminuted by chewing or otherwise, be
rendered quite digestible. Such articles are indigestible essentially
by reason of their compactness; the compact lumps, but little pervious
to the gastric juice, tend to undergo abnormal chemical change in the
stomach, and may in this way cause violent local irritation, even to
the extent of setting up acute gastritis; or they may paralyse the
nerves of the stomach and check gastric secretion and movement, and
thus remain _in loco_ wholly undigested for hours or even days; or,
again, more distant nervous effects may be produced, such as frontal
headache, which may be felt almost immediately after ingestion of
the peccant substance, being of reflex rather than toxic origin,
and presumably in some cases, at least, due to the mere mechanical
irritation of the stomach. The passage of imperfectly digested food
into the bowel may still further aggravate matters. It does not seem
improbable that the habitual bolting of food, by the prolonged local
irritation to which it gives rise, may predispose to cancer of the
stomach: Napoleon was a notorious fast eater and it is well known that
he died from this disease.
While, however, the bolting of food readily sets up disturbance in
some, it must be conceded that in many it seems to cause little or no
inconvenience; especially is this the case in the young with vigorous
muscular stomachs capable of triturating the food, and thus doing duty
for the teeth. The human stomach is, indeed, a long-suffering organ,
and wonderfully tolerant of ill-treatment, sometimes almost rivalling
in its hardiness the gizzard of the bird. Nor is this surprising when
we reflect that it is, in the ordinary course of nature, constantly
exposed to the entrance of noxious substances. In this respect it
stands in marked contrast to the intestines, for not only are highly
irritant substances often vomited rather than passed onwards, but in
ordinary circumstances the gastric contents are not allowed to pass
the pylorus, until they have been duly prepared by the stomach; the
pylorus, in fact, stands guard over the entrance to the bowel and is
jealous of anything passing it which is likely to injure that canal.
And just as the pylorus protects the bowel so, in exceptional cases,
may the œsophagus protect the stomach, regurgitating, after the fashion
of the ruminants, insufficiently masticated bits of food, in order
that they may be re-masticated. I have myself met with cases in point.
Sometimes, in cases of this kind, the œsophagus may be dilated into a
sort of proventriculus, which is capable of temporarily lodging a large
quantity of food. Such a proventriculus is said to have developed in
an apprentice who, not being allowed sufficient time for his dinner,
rapidly bolted it, to regurgitate it after working hours and to chew
the cud at leisure. Whether in these cases the food is ever returned
from the stomach itself I am unable to say.
While the stomach is the organ especially liable to be injured by the
swallowing of lumps of unmasticated food, the bowel may also suffer,
especially the cæcum and vermiform appendix. And here we come to one of
the most serious indictments against the bolting of food; though man
has doubtless always suffered from appendicitis, there can be little
doubt that this malady is more common now than it used to be; and
there is equally little doubt, in my own mind at least, that the cause
of its greater frequency is related to his food. I do not propose to
discuss here in detail how food is capable of causing appendicitis,
but will merely refer to one of the ways in which it may do so. I had
already come to the conclusion that the habit of bolting food is a
potent cause, when I read Sir Frederick Treves’s Cavendish Lecture in
which he makes that contention. Sir Frederick Treves points out that
in this rushing age people, especially business men, are apt to hurry
over their meals and to take them at irregular times and often while
standing at a bar; even when there is more leisure, food is rarely
masticated nowadays in the same thorough way that it was in the old
time, when it was of a coarser nature: hence solid lumps, especially
in the case of such articles as pine-apple, preserved ginger, nuts,
tough meat, and lobster, are apt to pass beyond the pylorus and,
escaping intestinal digestion, to lodge in the cæcum and precipitate an
attack of appendicitis, the most common predisposing cause of which is
a loaded cæcum, often preceded by constipation. Sir Frederick Treves
contends that this distended state of the cæcum encourages catarrh of
the appendix by dragging upon it and blocking its orifice, as well as
by twisting it and thus interfering with its blood-supply.[22]
_An excess of starch is apt to pass into the stomach._--We have just
seen that inefficient mastication tends to promote over-eating, and
what has been said on this head applies to all kinds of food, starchy
foods among others. It leads, however, to a further evil as regards
these latter; not only does it tend unduly to increase the quantity of
them consumed, but it too often causes the stomach and intestines to
become flooded with starch in a wholly undigested form. I cannot too
frequently repeat that in ancient times, especially in the pre-cooking
age, laborious mastication was needed in the case of all starchy
foods, partly because they were coarse and fibrous, but chiefly because
the starch and other nutritive ingredients had, in order to become
available for nutrition, to be liberated from their undigestible
cellulose envelopes. In these days of prepared, soft, starchy foods,
however, mastication is very little required for these purposes, but in
other respects it is as needful as ever, indeed more needful, if the
large quantities of starch which are now consumed are to be insalivated
effectually. The laborious and sustained mastication to which primitive
man was compelled to subject _his limited supplies of uncooked starchy
food, went far to effect complete digestion of the starch within the
mouth_, for raw starch is freely digested by the saliva,[23] and hence
in his case _very little passed into the stomach in a wholly undigested
form_. How different is the case with us moderns. Since the opening
of the era of agriculture and cooking, man has enormously multiplied
his supplies of saccharide, and he now consumes large quantities of
starch which has been freed from its cellulose framework by cooking,
milling, grinding, and the like, and reduced to a soft or pappy form,
such as milk puddings, porridge, boiled potatoes, and new bread, all
of which can be swallowed with little or no preliminary chewing; and
when food can be swallowed easily, without mastication, few will take
the trouble to masticate it. In these circumstances the starch does not
undergo adequate salivary digestion, and a large quantity passes wholly
undigested into, and out of, the stomach, not beginning to be digested
until it reaches the bowel. Small wonder that the latter should rebel
again this invasion and that flatulence, pain, and other dyspeptic
evils should result.
It is especially in young children that these evils are observed. Too
often the stomach of the child, semi-carnivorous, remember, by its
ancestry, is literally deluged with pure starch. At the seventh or
eighth month, or even earlier, for many of the patent infant foods
contain it, this substance is poured into the stomach without being
afforded any opportunity of undergoing salivary digestion; and for a
long time after infancy large quantities are given in the liquid or
pultaceous form, such as rusks soaked in milk, puddings, and mashed
potatoes. This practice of deluging the digestive organs with starch,
besides leading to the more immediate troubles connected with flatulent
dyspepsia, gives rise to abundant formation of toxins which, by
irritating the alimentary mucous membrane, set up gastro-intestinal
catarrh; this, again, intensifies the dyspepsia already existing and
causes a still further production of toxins, so that the motions
become intensely fœtid. These poisons being absorbed into the blood
the tissues become saturated with them and the nutrition of the entire
organism is disturbed, the faulty metabolism manifesting itself by a
diminished resistance to pathogenic agencies, by a tendency on the part
of the tissues to inflame (as shown by a liability in children thus fed
to bronchitis, rhinitis, naso-pharyngitis, and tonsillitis), by their
proneness to tuberculosis, and finally by a disposition to rickets,
which I little doubt is essentially of toxæmic origin.
Besides the above-mentioned troubles an excess of starch in the stomach
may set up hyperchlorhydria--_i. e._, that form of dyspepsia in which
there is excessive secretion of hydrochloric acid. This affection
occurs during the most vigorous years of life and is apparently due
to excessive activity on the part of the gastric glands. The excess
of acid does not give rise to any symptoms so long as there is any
unsatisfied proteid in the stomach to unite with it, but directly all
the proteid is satisfied and free acid is present in the stomach, pain,
heartburn, and distention are apt to be felt; hence these symptoms
are generally removed temporarily by a meal, the food ingested seizing
upon the free acid, and tend to recur in the course of an hour or
two. Other symptoms are mental and bodily lassitude and great mental
depression, while, if the condition is long-continued, gastric catarrh
and dilatation ensue. Eructation of the acrid mass, its removal with a
tube, or its dilution or neutralisation by an alkali, causes relief of
the symptoms. Now Dr. William Russell, who has recently studied this
form of dyspepsia, has shown, and the fact is most significant from
our present point of view, that in it starch is the last constituent
to leave the stomach; that when this organ has so far emptied itself
as to contain but one or two ounces of very acrid material the
residue consists chiefly of finely divided undigested starch, which
continues to stimulate the gastric secretion; “and, there being no more
proteid with which to combine, the secretion accumulates and leads to
hyperacidity.”[24] Inasmuch, then, as inefficient mastication leads to
an excess of starch in the stomach, we see how it may predispose to
hyperchlorhydria and we shall presently see that there is yet another
reason why it should do so.
It will be gathered from the foregoing that thorough mastication is
the most effective way of securing efficient starch digestion. This
simple fact has been most strangely overlooked. Thus “van Valzah
considers that not a little of the difficulty of the digestion of
starches and cereals can be overcome by more thorough cooking. Patients
who cannot eat potatoes after ordinary cooking are [he urges] often
able to digest them very readily if they are doubly cooked before
being served. Cereals, as a rule, should [he contends] be allowed to
simmer all night and then be thoroughly cooked for a half hour in the
morning before being eaten.”[25] This is an admirable illustration of
the modern tendency to cheat the mouth of its proper work. A much more
rational way of facilitating starch digestion in those who experience a
difficulty in this respect is by efficient mastication.
_Evils resulting from an insufficient quantity of alkali in the
stomach._--I doubt if it is adequately realised what a large amount
of alkaline saliva passes into the stomach as the result of prolonged
mastication. Its presence there serves the useful purpose of prolonging
the period of starch digestion within the stomach, while it further
aids gastric digestion not only by exciting the secretion of gastric
juice, but also by its influence on the reaction of the gastric
contents; it can scarcely be doubted that the effect is on the
whole one favourable to digestion in general. We have just seen that
defective mastication may predispose to hyperchlorhydria by allowing an
excess of pure starch to pass into the stomach, and I suggest that it
may further operate in the same direction by cheating the stomach of
its due supply of alkaline saliva. Now the saliva in this affection is
apt, as was pointed out by Sir William Roberts, to be superalkaline,
and for this reason he recommended his acid-dyspeptics to excite the
flow of it by chewing gum-mastic with the object of neutralising the
gastric hyperacidity. That relief can thus be obtained there can be no
doubt; but it is surely more rational to get the patient to stimulate
his salivary glands by masticating actual food, by which we secure
the additional advantages accruing from its complete insalivation and
comminution as well as from the reflex gastric effects. Actuated by
these considerations, I have long been in the habit of recommending
hyperchlorhydriacs to subject their food to prolonged mastication, this
being, in my belief, the most rational and effective way of breaking
the stomach of its vicious habit. In extreme cases we must insist that
each morsel of food should be chewed at least one hundred times and not
permit any relaxation of this severe discipline, until the stomach has
been schooled into healthier ways. _Evils in connection with the jaws
and their appendages and the adjacent structures: the nasal passages,
naso-pharynx, and faucial tonsils._--In those who do not masticate
properly in early life these parts fail to develop as they should,
and they are on this account alone predisposed to disease; their
resistance to disease is still further lowered by the fact of their
blood and lymph flow not being adequately stimulated by the vigorous
exercise of the masticatory muscles. Now we have seen that the great
cause of defective mastication in children is the softness of the food
given them and that the feeding of them upon an excess of soft food,
especially the starchy kind, disturbs digestion, induces toxæmia, and
in this way evokes a catarrhal tendency. In children thus fed we have
therefore several conditions which make for disease in the parts under
consideration--defective development, sluggish circulation, and toxic
saturation. Is it any wonder that the modern child should be liable
to disease in these regions, that he should so frequently suffer from
rhinitis, naso-pharyngitis, tonsillitis, and from hypertrophy of the
pharyngeal tonsil (“adenoids”) and of the faucial tonsils?
It is in this way that I would explain the frequency of adenoids among
the children of civilised communities. I claim, in fact, that this
disease is largely dietetic in origin. I submit that a child whose
nasal apparatus and naso-pharynx are well-grown and habitually bathed
by a stream of pure blood and lymph, periodically accelerated by an
ample and vigorous use of the masticatory muscles, is unlikely to
contract adenoids. On the other hand, I contend that a child in whom
these parts are ill-developed and bathed by an habitually sluggish
stream of tainted blood and lymph--one, _i. e._, that is not only
poisoned, but rarely, if ever, hurried along its lazy course by due
exercise of the muscles of mastication--I submit that such a child
runs great risk of contracting the disease. The influence in setting
up adenoids of toxic saturation with its resulting catarrhal tendency
is shown by the frequency with which this affection follows upon the
rhinitis and naso-pharyngitis of measles and diphtheria, and in order
to realise how greatly the circulation of blood and lymph in the walls
of the naso-pharynx must be influenced by mastication, one has but to
remember how very closely the pterygoids are related to this region; in
exploring it for adenoids they can, indeed, often be felt to stand out
prominently.[26]
This, then, is my explanation of the truly fearful prevalence of
adenoids among the moderns. It is essentially a disease of pap-fed
peoples. A child may, with the one exception that he is fed on a pappy,
super-saccharide diet, be brought up under ideal health conditions. He
may live in the heart of a dry, open country, far from the darkness,
dust, and tainted atmosphere of the town, sleep with the windows open
all night, live out of doors all day, be fed on the most nourishing
(too nourishing, it may be) food, be clothed after the most approved
methods, and yet, in spite of all this, we may find his naso-pharynx
packed with adenoids. This disease is, in fact, scarcely less prevalent
in the country than in the towns, scarcely less common among the rich
than among the poor. Yet in primitive communities it is practically
unknown. And what, I would ask, is the one condition in the material
environment of my supposititious child differing from that of the
primitive child? What but the factor of diet? Therefore, I say, the
prevalence of adenoids among moderns must be the result of the modern
system of feeding children, and the defective mastication which goes
along with it.
That the foregoing is a grave indictment against that system, it
need scarcely be said. For adenoid disease is fraught with many
evils, among them mental hebetude, blocking of the Eustachian tubes,
and manifold other auditory troubles, gastro-intestinal disturbances
from the passage into the stomach of unhealthy discharges, and, most
serious of all, nasal obstruction and consequent mouth-breathing.
So serious are the evils connected with this latter habit that they
demand more than a passing reference. Pronounced adenoid disease is
always associated with mouth-breathing, and there can be no doubt that
in the majority of these cases, the nasal obstruction is not in the
nasal passages primarily, but is due to a blockage of the posterior
nares by the adenoid growths, for it generally happens that nasal
breathing is rapidly re-established after their removal, though in a
certain proportion of cases the obstruction still persists, and has to
be dealt with by treatment directed to the nasal passages themselves.
Some have, indeed, contended that a primary nasal obstruction is one
important factor in the induction of adenoids, leading as it does to a
dry-cupping of the naso-pharynx during inspiration and to a consequent
congestion of its lining membrane. I am quite ready to allow that this
mechanism may play some part in causation, and such an assumption is
in entire harmony with my main contention that adenoid disease is of
dietetic origin, for nasal obstruction in children, other than that
caused by adenoids, is mainly due to defective development of the nasal
passages coupled with inflammation of their lining membrane, both of
which conditions may, as we have seen, be essentially the outcome of
defective diet.
Coming now to the evils resulting from mouth-breathing, we have first
to remember that normally the air is inhaled through the nose, and
is thus warmed, moistened, and filtered before being allowed to pass
into the lungs; but in the mouth-breather the air, which may be dry,
cold, and dust-laden, passes at once unprepared through the mouth into
the lungs, impinging in its passage against the pharynx, thus drying
and mechanically irritating the mouth, pharynx, larynx, and bronchial
tubes, all of which are thereby predisposed to disease. In this way
laryngitis and bronchitis, nay, even phthisis, may be induced. Dental
caries is also predisposed to by the habit of breathing through the
mouth. Mouth-breathing further interferes with the proper development
of the cranial bones, but especially of the maxilla, giving rise to
what may be termed the “mouth-breather’s jaw,” so characteristic is
it I do not propose to discuss here the mechanism by which this
deformity is produced, interesting though the question is; suffice it
to say that nasal breathing is essential to the normal development of
the jaws. The deformity in question, though it involves the maxilla
chiefly, affects also the mandible from the fact of its being, to a
large extent, moulded on the maxilla; in typical cases the maxilla is
small and its alveolar ridge does not attain its normal length, but is
compressed laterally towards the sagittal plane, giving rise to the
false appearance of a “high arch” and often thrusting the anterior
portion of the ridge forwards; the teeth, the growth of which is not so
much interfered with as that of the imbedding bone, are thus prevented
from taking up their proper positions and show irregularity, sometimes
extreme. Dental irregularity may also, as we shall see, result from
inadequate use of the jaws in mastication, but not to the extent which
is frequently observed in the mouth-breather’s jaws, and therefore
pronounced dental irregularity always shows that there has been
protracted nasal obstruction, and this in the vast majority of cases
implies the existence of adenoids, past or present; I say in the “vast
majority,” for in a few rare cases long-continued nasal obstruction in
children originates primarily in the nose and may lead to the typical
mouth-breather’s jaw, with the resulting dental irregularity.
_The tongue._--If the tongue is not properly exercised in childhood
and youth, we find it imperfectly developed; hence in inefficient
masticators it is generally small. It must not be forgotten in this
connection that this organ is considerably exercised when the infant
is at the breast, from which the milk is obtained, not by suction,
but by a vigorous tugging and squeezing of the nipple (in which the
tongue takes considerable part), whereby the gland is reflexly excited
to secrete. When, on the other hand, the child feeds at the bottle he
obtains his milk by actual suction, and generally through an orifice
of such ample dimensions as to allow the bottle to be rapidly emptied
with comparatively little exercise of the lips and tongue. In short,
the breast-fed infant has to do some work for his living, and that of a
sort calculated to promote the health of the jaws and their appendages,
while the bottle-fed child can glut himself by doing very little more
than opening his mouth; wherefore we find the tongue and adjacent parts
less developed in the latter than in the former. It may be thought to
be a matter of indifference whether the tongue develops to its normal
proportions or remains small, but such is by no means the case, for, as
Dr. J. Sim Wallace has shown, the pressure of this structure against
the teeth promotes the normal development of the jaws, especially of
the mandible, and when it is small they are apt to be so too.
_The salivary glands._--Just as mastication increases the functional
activity of the salivary glands and buccal glands and favours their
normal development, so, contrariwise, inefficient mastication during
early life fails to call forth their normal functional activity and
to secure their adequate development. Thus we find that a child who
has been brought up on hard, starchy foods, necessitating abundant
mastication has much larger and more active salivary glands than
one who has been fed on soft foods which slip down into the stomach
before they have had the chance of being properly masticated, and it
is needless to say that the more efficient these glands are the more
likely is digestion to be carried out satisfactorily.
_The jaw-bones._--If the jaws are not adequately exercised in youth
by mastication they fail to grow to their normal size and shape, and
there is apt in consequence to be overcrowding of the teeth. The main
defect of the jaws in such cases is their smallness; they do not
present that pronounced lateral compression and anterior protrusion
which characterise the mouth-breather’s jaw, nor such extreme dental
irregularity, the most common being overlapping of the incisors,
displacement of the canines, and difficulties in regard to the eruption
of the wisdom teeth from shortness of the alveolar ridge. I have
already referred to the progressive shortening in the post-molar ridge,
which has been taking place during man’s evolution from the anthropoid
in correspondence with the alteration in his diet.
We thus see that defective use of the jaws leads to irregularity of
the teeth (1) directly and (2) indirectly through the induction of
adenoids. This irregularity is not only unsightly but leads to certain
evils which thus primarily owe their origin, in large measure at least,
to defective mastication. What, then, are these evils? In the first
place, dental irregularity predisposes to dental caries by favouring
the lodgement of food between the teeth; in the next place, it leads to
defective “bite.” Now when the bite is defective adequate mastication
is impossible, for not only is it impossible in these circumstances
to oppose the teeth properly, but also, owing to their interlocking,
to accomplish that free lateral movement of the lower teeth against
the upper, which belongs to normal mastication. I do not say that
defective bite is the sole cause of this imperfect lateral movement;
it may, indeed, be observed in most moderns brought up on soft pappy
food, whether the bite be good or not. Normal mastication is, in fact,
becoming a lost art; the average modern masticates mainly by a vertical
compression of the lower teeth against the upper, and in only a small
degree by a lateral frictional movement which, it is needless to say,
is the more effective method for grinding purposes; and it is, I doubt
not, chiefly for this reason that the teeth of modern man are so much
less worn down than those of primitive peoples.
_The teeth._--Imperfect use of the teeth leads to many ills. When
adequately exercised and made to execute for one or two hours every day
a lively dance in their sockets, during which the circulation of blood
and lymph in the tooth-pulp, periodontal membrane, and surrounding
tissue of the gum is vigorously stimulated, and the cavity of the mouth
is bathed in a copious flow of salivary and other buccal secretions, we
have conditions which make alike for the health of the buccal mucous
membrane, of the teeth, and of the periodontal membrane and alveoli;
but when the circulation is not duly stimulated in this way the teeth
do not develop properly, while the secretions of the mouth are apt to
be scanty and unhealthy, both of which conditions predispose to caries.
How far dental caries is due to inherent dental weakness and how far
to faulty conditions outside the teeth we need not stop to inquire; Dr.
Wallace attributes little influence to the former factor, contending
that caries depends essentially upon faulty dental environment; and
one can scarcely doubt that the state of the gums and of the oral
secretions profoundly influences the growth of bacteria in the mouth,
upon the acid yielded by which organisms the corrosion of the dental
enamel essentially depends. Faulty conditions of the oral secretions
likewise favour the deposit of tartar.
Another result of imperfect use of the teeth is undue thinness of
the alveolar walls and periodontal membrane, in consequence of which
the teeth are not so firmly held in their sockets as they should be.
This is, I believe, one of the reasons why they are prone to fall
out prematurely among the moderns: we know that the teeth tend to
drop out in old people owing to a senile atrophy of the alveolar
walls; the Haversian canals get smaller and may, indeed, disappear
entirely, and it stands to reason that this atrophy must be hastened by
inefficient exercise of the teeth. So far as I am able to gather from
an examination of skulls in museums, the teeth are rarely shed among
primitive peoples before extreme old age, while among moderns they
frequently fall out long ere this is attained.
A still worse evil attaching to insufficient use of the teeth is
pyorrhœa alveolaris or Riggs’s disease, which, in conjunction with the
deposit of tartar, is the great cause of the premature loosening and
shedding of the teeth observed among latter-day civilised peoples.
This affection consists of a purulent inflammation of the periodontal
membrane, owing to the invasion of it by pyogenic cocci, so that pus
wells up on pressing the gum against the teeth. Now, when by a vigorous
use of the teeth the buccal cavity is kept well flushed with healthy
secretions, the growth of micro-organisms within this chamber is kept
down, and when, by the same means, the vitality of the periodontal
membrane and adjacent tissues of the gum is periodically stimulated,
these tissues offer stout resistance to the invasion of pathogenic
organisms; but when, contrariwise, the teeth are little used, the
secretions of the mouth are in consequence defective both as to
quality and quantity, and the growth of organisms in the buccal cavity
is promoted; and when, further, the circulation in the periodontal
membrane and adjacent soft tissues is not adequately stimulated by
vigorous mastication, their vitality is poor and they offer but a
feeble resistance to parasitic invasion. We can thus, I think, safely
infer that inefficient mastication is a potent cause of pyorrhœa
alveolaris; and the chief cause of inefficient mastication being the
eating of soft foods, we must also conclude that the latter practice
is chiefly responsible for the disease in question; such foods further
predispose to this affection in that they are apt to lodge between
the teeth and by undergoing decomposition there to favour the growth
of micro-organisms within the mouth. The condition of the teeth and
gums among the civilised poor is, alas, little calculated to make us
proud of our boasted civilisation--the spongy pus-exuding gums, the
lengthening, loose, tartar-covered, carious teeth, and the putrescent
breath constitute a damning indictment against our modern system of
living on a soft, pappy diet, and not giving the teeth the work for
which they are designed. I never examine such a mouth without being
impressed with, and I may add oppressed by, this fact.
I am not, of course, contending that pyorrhœa alveolaris only occurs
in those who masticate inefficiently; whatever causes an unhealthy
condition of the gums and saliva predisposes to it, but it is surely
much less common in those who masticate well than in those who
masticate ill. Confirmatory of this statement is the fact that it is
more frequent in those with irregular teeth than in those with a good
bite, who are thus able to put their teeth to more effective use. This
affection is very common among the carnivora of menageries as well as
among dogs and cats; indeed, one seldom fails to find it in dogs over
four years of age, and in old dogs it is generally rampant. Doubtless
in all these cases the general conditions of life play some part in
the causation of the disease, but I do not think that we can eliminate
from it the factor of defective use of the jaws and teeth, for it is
certain that dogs and cats are fed largely on pappy foods and are often
insufficiently supplied with bones.
_The causation of dental caries._--Dr. Wallace, in his philosophical
work on “The Cause and Prevention of Decay in Teeth,” contends that
the cause of the prevalence of dental caries is that the natural
food-stuffs are, to a large extent, ridded of their accompanying
fibrous parts and consumed in a form which renders them liable to
lodge and to undergo acid fermentation in the mouth; while from the
same cause and the induced conditions the micro-organisms of the mouth
lodge and multiply and augment the rapidity and intensity of the acid
fermentation. I am perfectly at one with Dr. Wallace in believing
that the removal of the fibrous portions of food is the main cause of
the prevalence of caries among moderns, and I can hardly doubt that
foods so prepared tend to promote caries in the way indicated, but I
venture to think that they do this even more by failing to call forth
the normal degree of mastication. I cannot but think that if these same
soft foods were as laboriously masticated as they would need to be if
they retained their fibrous ingredients, dental caries would be much
less common than it actually is. I have endeavoured to show how very
different the local conditions are in the efficient from what they are
in the inefficient masticator--how in the former the jaws and teeth
are wont to be well developed, the bite to be good, and the secretions
which bathe the teeth to be of a kind calculated to promote their
health; and how in the latter an entirely opposite set of conditions is
wont to prevail. That it is possible to maintain a fine set of healthy
teeth till past middle life on ordinary civilised diet, provided the
food be habitually subjected to efficient mastication, is shown in the
case of the man already referred to, and by numerous other cases which
I have observed.
Since the application of cooking to food there has been a progressive
lessening in the work of the jaws and teeth and, parallel with this,
a diminution in their size and an incursion of dental caries. Among
the anthropoids in their natural state caries is practically unknown,
and I think we may conclude that the same was true of man before he
learnt to cook. In the pre-agricultural races, such as the aboriginal
Australians, the effect of cooking the food is shown in the lessening
in the size of the wisdom teeth and of the post-wisdom alveolar
ridge; dental caries, though rare among these people, does occur, and
especially in the wisdom teeth.[27] In the early agricultural period,
owing to the increasing softness of the vegetable food, the jaws and
teeth show a tendency to be smaller than in the previous periods; the
wisdom teeth are decidedly smaller and more prone to caries, while
caries of the other teeth is by no means rare. In the late agricultural
period the jaws and teeth often show very decided defects of
development, while dental caries is, as we know but too well, rampant.
What has been said concerning the relative prevalence of caries in
different diet epochs applies to many other diseases of the teeth;
thus, along with the increase of caries, there has been a parallel
increase in the prevalence of pyorrhœa alveolaris.
CONCLUDING REMARKS
I have now set forth some of the evils resulting from inefficient
mastication. They are many and serious. The immediate evils, such
as over-eating, indigestion, adenoids, dental caries, and pyorrhœa
alveolaris, are bad enough, but when we consider the secondary evils
to which these primary ones give rise,--and I have only mentioned a
few of them,--we must come to the conclusion that an appalling amount
of misery and suffering may be saved by the simple expedient of
inculcating the habit of efficient mastication. How this end can best
be accomplished will be considered in the next section.