Part 9
_Mastication in the industries._--Even among moderns teeth are used for many purposes other than mastication--_e. g._, for holding pins and needles and for severing cotton; also in some industries--_e. g._, among diamond workers--where it is the custom for girls to hold the diamond between their front teeth, which in consequence get much worn away, as I have myself seen. It is only among primitive peoples, however, that the jaws and teeth actually play the part of implements for use in the arts. The Australian women make lines, nets, and bags by chewing various kinds of fibre, a process which wears down their teeth considerably and may cause them to be tender.[13] The Esquimaux are still more dependent upon the use of their teeth as implements, especially in the preparation of skins for their clothing, boats, and lines. The teeth are used to hold the skins, while the latter are being scraped, the mouth constituting, in fact, “a third hand;” and the front teeth of Esquimaux women are often by this means worn away to the merest stumps.[14] The garments of the Esquimaux, even to the boots, are made up of skins which have been laboriously chewed for this purpose by the women “inch by inch,” till they acquire a beautiful softness and flexibility, and are often, indeed, chewed again after having been dried. And we are told that the women have no objection to the task, while the children are eager to help in it on account of the blubber the skin contains; also, that in bad times the men do not object to join in the work. The lines for harpooning are prepared in a similar way from the skin of the bearded seal, and in very large quantities.[15] When we think of the quantity of skins needed for these lines, for their dress, including boots and gloves, and for their boats (although for the latter some skins are used without having first undergone chewing), it is clear that enormous quantities must be chewed. The Esquimaux men also use their teeth considerably in other work--_e. g._, in lashing the sledges together.[16] The Indians of North California use their teeth for stripping the bark from the fresh shoots employed in making their wickerwork utensils, and they also employ their teeth in making strings, cords, and nets.
THE INSTINCT TO MASTICATE
Seeing that the maxillary apparatus of man has for long ages past been put to vigorous use, it is not surprising that the need to exercise it should express itself as a powerful instinct. This instinct manifests itself in many and curious ways, some of which I will now consider. During the early months of life the natural function of feeding at the breast provides the infant’s jaws, tongue, and lips with all the needful exercise. This bottle-feeding fails to do, and we frequently find bottle-fed children seeking to satisfy the natural instinct by sucking their thumb, fingers, or any convenient object to hand. The teeth are a provision for biting hard foods, but even before they actually appear we find the child seeking to exercise his toothless gums on any hard substance he can lay hold of, and there can be no doubt that exercise of this kind tends to facilitate the eruption of the teeth, a truth, indeed, recognised universally, whether by the primitive mother who strings the tooth of some wild animal round the neck of her infant, or the up-to-date parent who provides her child with a bejewelled ivory or coral bauble. When the teeth have erupted, the masticatory instinct finds among primitive peoples abundant satisfaction in the chewing of the coarse, hard foods which constitute their dietary; but among us moderns, subsisting as we do mainly on soft foods, affording but little exercise for the masticatory apparatus, it does not find its proper expression, and thus tends to die out. Nevertheless, it dies a hard death, and long continues to assert itself; witness the tendency of children to bite their pencils and pen-holders; I have known a child to gnaw through a bone pen-holder, much in the same way as a carnivorous animal gnaws at a bone.
This instinct to chew for chewing’s sake manifests itself all over the world. In our own country not only do children bite pencils and pen-holders, but they will chew small pieces of india-rubber for hours together. The practice of gum-chewing, so common among our American cousins, evidently comes down from far-off times, for the primitive Australians chew several kinds of gum, attributing to them nutrient qualities,[17] and the Patagonians are said to keep their teeth white and clean by chewing _matri_, a gum which exudes from the incense bush, and is carefully collected by the women and children.[18]
A widespread custom in the East is betel-chewing, which is met with in India, Malay, Melanesia, and Polynesia, and even among the primitive Veddahs of Ceylon. This article is composed of the pungent leaf of the betel plant, the areca nut and lime rolled together, and when chewed yields a reddish juice which stains the mouth and teeth. The Veddahs, failing to get the genuine article, manufacture a quid from the leaves of an aromatic plant, the barks of one or two kinds of tree, and calcined small shells.[19] The compound must possess some strange attraction, for otherwise such pains would not be taken to secure it. What is the attraction? Doubtless betel has stimulating properties, and it must, moreover, be remembered that the mere mechanical act of mastication stimulates the circulation, a fact which helps to explain the tendency for man, all the world over, to chew non-nutrient substances. Tobacco-chewing is common in many parts of the world, and here, again, the effect for the time is stimulating. Pitcherie is extensively chewed among the aboriginal Australians; it consists of twigs of about the thickness of rye-grass stems, which are first chewed into a mass, then mixed with the ash of gum trees, and made into a paste, which is chewed for its stimulating and narcotic effects.[20]
I may allude in passing to the grinding of the teeth, which takes place during sleep in disturbed states of the nervous system. It is a true masticatory act, in which the normal lateral movement of the mandible is well marked, and it may thus be regarded as a perverted manifestation of the masticatory instinct.
THE CAUSATION OF INEFFICIENT MASTICATION
The effects for good upon the organism of efficient mastication being profound and far-reaching, it follows that inefficient mastication must lead to many evils. What these are we have now to consider; but first it will be well to inquire into the causes of the defective mastication which prevails among moderns.
1. _Softness of food._--By far the most important of these lies in the nature of the food taken. The food of to-day--of the late agricultural age period, as I have termed it--is for the most part soft and pappy, of a kind which does not compel thorough mastication; so much so, indeed, that, as I have already said, we may speak of this as the age of pap. This feature is especially noticeable in the case of children’s diet: under the modern system children are kept on a liquid, or semi-liquid, diet, not merely during the first months, but during the first years of life, and at the seventh or eighth month all kinds of artificial saccharide foods in liquid or semi-liquid form are poured into the child’s stomach; thereafter he is fed on such viands as mashed potatoes and gravy, rusks soaked in milk, milk puddings, bread dipped in bacon fat, pounded mutton, thin bread-and-butter, and the like; and we are told that this is the kind of diet best suited to the young human, from the time of weaning to the end of the second year! The same pernicious methods are adopted subsequently. “Perhaps the great majority of children after they have got their complete set of temporary teeth have,” writes Dr. Sim Wallace,[21] “a dietary such as the following. Breakfast: bread-and-milk or porridge, milk, tea, coffee, or cocoa, bread-and-butter, perhaps an egg. Dinner: potatoes and gravy, or meat, milk pudding. Tea: milk or tea with bread-and-butter, jam, cakes. Supper: bread or biscuit and milk.” Now food of this kind does not invite mastication, and it finds its way into the stomach all too readily. Hence the instinct to masticate has little opportunity of exercise and, not being properly exercised, tends, as I have said, to die out. Small wonder that the child nourished on such pappy food acquires the habit of bolting it, and learns to reject hard, coarse foods in favour of the softer kinds; everything nowadays must be tender, pultaceous, or “short.” Given a choice between a food compelling little or no mastication and one necessitating prolonged mastication--as between, say, fresh Vienna bread and an Abernethy biscuit--and in nineteen cases out of twenty the one which gives the least trouble in eating will be chosen. To such absurd lengths has this harmful custom been pushed that even bread crust is avoided by many. Witness the fashion of eating bread-and-butter with a minimum of crust; order bread-and-butter at any place of refreshment, and the last thing you will be served with is a plateful of crusts of bread. Many establishments, indeed, make a regular practice of giving away their crusts as unsaleable. Thus, the rectangular loaves used for bread-and-butter in the “Aërated bread-shops” are cut transversely into slices, each loaf thus yielding two end crusts which are put into baskets for the poor, only the soft crumby pieces being reserved for the customers, to be, in due course, no doubt washed down by copious libations of tea and coffee.
When we trace the diet of the modern from childhood upwards we find the same story: it tends to remain soft and pappy to the end. Animal food, especially as it comes to the tables of the well-to-do, necessitates very little mastication. It is the coarser varieties of vegetable food alone which call out the full functional activity of the masticatory apparatus, but the vegetable food of to-day is rarely of a kind to do this; cooked vegetables, such as potatoes, greens, peas, and beans, can be, and generally are, swallowed after little or no preliminary mastication, and our flour is so carefully deprived of its fibrous portions and so cunningly dealt with in the bakehouse and kitchen in the making of bread, cakes, and pastry which shall eat light and short that these articles get very little chewing; while such vegetable products as rice, vermicelli, tapioca, and macaroni are, as served at table, so soft that they slip down into the stomach almost as readily as simple milk. Let any one run through his dietary of any one day, and he will realise how very little work his masticatory apparatus is called upon to perform. It will read something like the following. Breakfast: porridge and milk, eggs, bacon, bread, and marmalade. Lunch: fish, tender meat, boiled vegetables, bread, some “sweet,” and cheese. Tea: bread, butter, and cake. Dinner: much the same as lunch. What opportunity, I ask, does such a bill-of-fare afford for the development of teeth and jaws, and for the proper functional activity of the salivary glands?
2. _Defective masticatory apparatus._--Another potent cause of inefficient mastication is some defect in the masticatory apparatus, and defects of this kind are very common in those who have not been accustomed to masticate thoroughly in early life. Foremost among these are irregularities of the teeth leading to faulty “bite” and caries of the teeth which causes them to be tender or to break away, if it does not lead to their actual extraction. Mastication cannot be thorough where the bite is defective, for this not only leads to imperfect opposition of the upper and lower teeth, but renders the lower ones incapable of that ample lateral movement, against the upper which is needful to normal mastication.
3. _Idiosyncrasy._--Some are temperamentally more disposed to hurry over their meals than others. The katabolic, restless, nervous individual is more apt to swallow his food hastily than is his more deliberate and phlegmatic brother. Individual differences in this respect are even observed among the lower animals. Thus, one of a pair of horses of about the same age and build is nervous and excitable and inclined to bolt its food, while its companion of more stolid temperament is a thorough and efficient masticator. The former shows comparatively little wearing down of the teeth, and often suffers from indigestion, a large portion of corn grains passing through his digestive canal intact; in the latter the teeth are well worn, indigestion never occurs, and but very few grains pass through the digestive tract unchanged. It may be objected here that we cannot help temperament, and to a large extent this is true; but much can be done towards modifying it, and it is something to know where dangers, temperamental dangers, among others, lie.
4. _Circumstances of life._--Again, in this hurrying, strenuous age people are much less deliberate than in the easy, slow-going days of long ago. A meal is too often regarded as something to be got through quickly, as taking up time which might be devoted to something more profitable. Especially is this true of breakfast and lunch; it is no uncommon thing for a business man to hurry through his breakfast in a few minutes, preparatory to rushing off to his train, and his lunch as likely as not is as hastily swallowed in his office or at a bar. Tradesmen are apt to take their meals in mere snatches; apprentices, shop girls, and other “hands” are often not allowed sufficient time for their meals; while, to come to the professions, we all know how the busy medical man, for instance, is often obliged to take a hurried snack in the short intervals between seeing his patients. No wonder that thus circumstanced people acquire the habit of bolting their food. A meal should be regarded as an end, and an important end, in itself. It should be taken at leisure, body and mind being, for the time being, given up to it, and to agreeable social intercourse. If this rule were always observed a most important source of inefficient mastication would be removed.
SECTION III. From _London Lancet_, July 25, 1903
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]