If we take too much drink with our meals, the flow of the saliva is checked, and digestion is hindered. It is not desireable to dilute the gastric juice, nor to chill the stomach with large amount of cold liquid.

Do not take food and drink too hot or too cold. If they are taken too cold, the stomach is chilled, and digestion delayed. If we drink freely of ice-water, it may require half an hour or more for the stomach to regain its natural heat.

It is a poor plan to stimulate a flagging appet.i.te with highly spiced food and bitter drinks. An undue amount of pepper, mustard, horseradish, pickles, and highly seasoned meat-sauces may stimulate digestion for the time, but they soon impair it.

[NOTE. The process of gastric digestion was studied many years ago by Dr. Beaumont and others, in the remarkable case of Alexis St. Martin, a French-Canadian, who met with a gun-shot wound which left a permanent opening into his stomach, guarded by a little valve of mucous membrane. Through this opening the lining of the stomach could be seen, the temperature ascertained, and numerous experiments made as to the digestibility of various kinds of food.

It was by these careful and convincing experiments that the foundation of our exact knowledge of the composition and action of gastric juice was laid. The modest book in which Dr. Beaumont published his results is still counted among the cla.s.sics of physiology. The production of artificial fistulae in animals, a method that has since proved so fruitful, was first suggested by his work.]

It cannot be too strongly stated that food of a simple character, well cooked and neatly served, is more productive of healthful living than a great variety of fancy dishes which unduly stimulate the digestive organs, and create a craving for food in excess of the bodily needs.

168. The Proper Care of the Teeth. It is our duty not only to take the very best care of our teeth, but to retain them as long as possible.

Teeth, as we well know, are p.r.o.ne to decay. We may inherit poor and soft teeth: our mode of living may make bad teeth worse. If an ounce of prevention is ever worth a pound of cure, it is in keeping the teeth in good order. Bad teeth and toothless gums mean imperfect chewing of the food and, hence, impaired digestion. To attain a healthful old age, the power of vigorous mastication must be preserved.

One of the most frequent causes of decay of the teeth is the retention of fragments of food between and around them. The warmth and moisture of the mouth make these matters decompose quickly. The acid thus generated attacks the enamel of the teeth, causing decay of the dentine. Decayed teeth are often the cause of an offensive breath and a foul stomach.

[Ill.u.s.tration: Fig. 64.--Lymphatics on the Inside of the Right Hand.]

To keep the teeth clean and wholesome, they should be thoroughly cleansed at bedtime and in the morning with a soft brush and warm water. Castile soap, and some prepared tooth-powder without grit, should be used, and the brush should be applied on both sides of the teeth.

The enamel, once broken through, is never renewed. The tooth decays, slowly but surely: hence we must guard against certain habits which injure the enamel, as picking the teeth with pins and needles. We should never crack nuts, crush hard candy, or bite off stout thread with the teeth.

Stiff tooth-brushes, gritty and cheap tooth-powders, and hot food and drink, often injure the enamel.

To remove fragments of food which have lodged between adjacent teeth, a quill or wooden toothpick should be used. Even better than these is the use of surgeon's floss, or silk, which when drawn between the teeth, effectually dislodges retained particles. If the teeth are not regularly cleansed they become discolored, and a hard coating known as _tartar_ acc.u.mulates on them and tends to loosen them. It is said that after the age of thirty more teeth are lost from this deposit than from all other causes combined. In fact decay and tartar are the two great agents that furnish work for the dentist.[26]

169. Hints about Saving Teeth. We should exercise the greatest care in saving the teeth. The last resort of all is to lose a tooth by extraction. The skilled dentist will save almost anything in the shape of a tooth.

People are often urged and consent to have a number of teeth extracted which, with but little trouble and expense, might be kept and do good service for years. The object is to replace the teeth with an artificial set. Very few plates, either partial or entire, are worn with real comfort. They should always be removed before going to sleep, as there is danger of their being swallowed.

The great majority of drugs have no injurious effect upon the teeth. Some medicines, however, must be used with great care. The acids used in the tincture of iron have a great affinity for the lime salts of the teeth. As this form of iron is often used, it is not unusual to see teeth very badly stained or decayed from the effects of this drug. The acid used in the liquid preparations of quinine may destroy the teeth in a comparatively short time. After taking such medicines the mouth should be thoroughly rinsed with a weak solution of common soda, and the teeth cleansed.

170. Alcohol and Digestion. The influence of alcoholic drinks upon digestion is of the utmost importance. Alcohol is not, and cannot be regarded from a physiological point of view as a true food. The reception given to it by the stomach proves this very plainly. It is obviously an unwelcome intruder. It cannot, like proper foods, be transformed into any element or component of the human body, but pa.s.ses on, innutritious and for the most part unappropriated. Taken even into the mouth, by any person not hardened to its use, its effect is so pungent and burning as at once to demand its rejection. But if allowed to pa.s.s into the stomach, that organ immediately rebels against its intrusion, and not unfrequently ejects it with indignant emphasis. The burning sensation it produces there, is only an appeal for water to dilute it.

The stomach meanwhile, in response to this fiery invitation, secretes from its myriad pores its juices and watery fluids, to protect itself as much as possible from the invading liquid. It does not digest alcoholic drinks; we might say it does not attempt to, because they are not material suitable for digestion, and also because no organ can perform its normal work while smarting under an unnatural irritation.

Even if the stomach does not at once eject the poison, it refuses to adopt it as food, for it does not pa.s.s along with the other food material, as chyme, into the intestines, but is seized by the absorbents, borne into the veins, which convey it to the heart, whence the pulmonary artery conveys it to the lungs, where its presence is announced in the breath.

But wherever alcohol is carried in the tissues, it is always an irritant, every organ in turn endeavoring to rid itself of the noxious material.

171. Effect of Alcoholic Liquor upon the Stomach. The methods by which intoxicating drinks impair and often ruin digestion are various. We know that a piece of animal food, as beef, if soaked in alcohol for a few hours, becomes hard and tough, the fibers having been compacted together because of the abstraction of their moisture by the alcohol, which has a marvelous affinity for water. In the same way alcohol hardens and toughens animal food in the stomach, condensing its fibers, and rendering it indigestible, thus preventing the healthful nutrition of the body. So, if alcohol be added to the clear, liquid white of an egg, it is instantly coagulated and transformed into hard alb.u.men. As a result of this hardening action, animal food in contact with alcoholic liquids in the stomach remains undigested, and must either be detained there so long as to become a source of gastric disturbance, or else be allowed to pa.s.s undigested through the pyloric gate, and then may become a cause of serious intestinal disturbance.[27]

This peculiar property of alcohol, its greedy absorption of water from objects in contact with it, acts also by absorbing liquids from the surface of the stomach itself, thus hardening the delicate glands, impairing their ability to absorb the food-liquids, and so inducing gastric dyspepsia. This local injury inflicted upon the stomach by all forms of intoxicants, is serious and protracted. This organ is, with admirable wisdom, so constructed as to endure a surprising amount of abuse, but it was plainly not intended to thrive on alcoholic liquids. The application of fiery drinks to its tender surface produces at first a marked congestion of its blood-vessels, changing the natural pink color, as in the mouth, to a bright or deep red.

If the irritation be not repeated, the lining membrane soon recovers its natural appearance. But if repeated and continued, the congestion becomes more intense, the red color deeper and darker; the entire surface is the subject of chronic inflammation, its walls are thickened, and sometimes ulcerated. In this deplorable state, the organ is quite unable to perform its normal work of digestion.[28]

172. Alcohol and the Gastric Juice. But still another destructive influence upon digestion appears in the singular fact that alcohol diminishes the power of the gastric juice to do its proper work. Alcohol coagulates the pepsin, which is the dissolving element in this important gastric fluid. A very simple experiment will prove this. Obtain a small quant.i.ty of gastric juice from the fresh stomach of a calf or pig, by gently pressing it in a very little water. Pour the milky juice into a clear gla.s.s vessel, add a little alcohol, and a white deposit will presently settle to the bottom. This deposit contains the pepsin of the gastric juice, the potent element by which it does its special work of digestion. The ill effect of alcohol upon it is one of the prime factors in the long series of evil results from the use of intoxicants.

173. The Final Results upon Digestion. We have thus explained three different methods by which alcoholic drinks exercise a terrible power for harm; they act upon the food so as to render it less digestible; they injure the stomach so as seriously to impair its power of digestion; and they deprive the gastric juice of the one princ.i.p.al ingredient essential to its usefulness.

Alcoholic drinks forced upon the stomach are a foreign substance; the stomach treats them as such, and refuses to go on with the process of digestion till it first gets rid of the poison. This irritating presence and delay weaken the stomach, so that when proper food follows, the enfeebled organ is ill prepared for its work. After intoxication, there occurs an obvious reaction of the stomach, and digestive organs, against the violent and unnatural disturbance. The appet.i.te is extinguished or depraved, and intense headache racks the frame, the whole system is prostrated, as from a partial paralysis (all these results being the voice of Nature's sharp warning of this great wrong), and a rest of some days is needed before the system fully recovers from the injury inflicted.

It is altogether an error to suppose the use of intoxicants is necessary or even desirable to promote appet.i.te or digestion. In health, good food and a stomach undisturbed by artificial interference furnish all the conditions required. More than these is harmful. If it may sometimes seem as if alcoholic drinks arouse the appet.i.te and invigorate digestion, we must not shut our eyes to the fact that this is only a seeming, and that their continued use will inevitably ruin both. In brief, there is no more sure foe to good appet.i.te and normal digestion than the habitual use of alcoholic liquors.

174. Effect of Alcoholic Drinks upon the Liver. It is to be noted that the circulation of the liver is peculiar; that the capillaries of the hepatic artery unite in the lobule with those of the portal vein, and thus the blood from both sources is combined; and that the portal vein brings to the liver the blood from the stomach, the intestines, and the spleen.

From the fact that alcohol absorbed from the stomach enters the portal vein, and is borne directly to the liver, we would expect to find this organ suffering the full effects of its presence. And all the more would this be true, because we have just learned that the liver acts as a sort of filter to strain from the blood its impurities. So the liver is especially liable to diseases produced by alcoholics. Post mortems of those who have died while intoxicated show a larger amount of alcohol in the liver than in any other organ. Next to the stomach the liver is an early and late sufferer, and this is especially the case with hard drinkers, and even more moderate drinkers in hot climates. Yellow fever occurring in inebriates is always fatal.

The effects produced in the liver are not so much functional as organic; that is, not merely a disturbed mode of action, but a destruction of the fabric of the organ itself. From the use of intoxicants, the liver becomes at first irritated, then inflamed, and finally seriously diseased.

The fine bands, or septa, which serve as part.i.tions between the hepatic lobules, and so maintain the form and consistency of the organ, are the special subjects of the inflammation. Though the liver is at first enlarged, it soon becomes contracted; the secreting cells are compressed, and are quite unable to perform their proper work, which indeed is a very important one in the round of the digestion of food and the purification of the blood. This contraction of the septa in time gives the whole organ an irregularly puckered appearance, called from this fact a hob-nail liver or, popularly, gin liver. The yellowish discoloration, usually from retained or perverted bile, gives the disease the medical name of cirrhosis.[29] It is usually accompanied with dropsy in the lower extremities, caused by obstruction to the return of the circulation from the parts below the liver. This disease is always fatal.

175. Fatty Degeneration Due to Alcohol. Another form of destructive disease often occurs. There is an increase of fat globules deposited in the liver, causing notable enlargement and destroying its function. This is called fatty degeneration, and is not limited to the liver, but other organs are likely to be similarly affected. In truth, this deposition of fat is a most significant occurrence, as it means actual destruction of the liver tissues,--nothing less than progressive death of the organ. This condition always leads to a fatal issue. Still other forms of alcoholic disease of the liver are produced, one being the excessive formation of sugar, const.i.tuting what is known as a form of diabetes.

176. Effect of Tobacco on Digestion. The noxious influence of tobacco upon the process of digestion is nearly parallel to the effects of alcohol, which it resembles in its irritant and narcotic character.

Locally, it stimulates the secretion of saliva to an unnatural extent, and this excess of secretion diminishes the amount available for normal digestion.

Tobacco also poisons the saliva furnished for the digestion of food, and thus at the very outset impairs, in both of these particulars, the general digestion, and especially the digestion of the starchy portions of the food. For this reason the amount of food taken, fails to nourish as it should, and either more food must be taken, or the body becomes gradually impoverished.

The poisonous _nicotine_, the active element of tobacco, exerts a destructive influence upon the stomach digestion, enfeebling the vigor of the muscular walls of that organ. These effects combined produce dyspepsia, with its weary train of baneful results.

The tobacco tongue never presents the natural, clear, pink color, but rather a dirty yellow, and is usually heavily coated, showing a disordered stomach and impaired digestion. Then, too, there is dryness of the mouth, an unnatural thirst that demands drink. But pure water is stale and flat to such a mouth: something more emphatic is needed. Thus comes the unnatural craving for alcoholic liquors, and thus are taken the first steps on the downward grade.

"There is no doubt that tobacco predisposes to neuralgia, vertigo, indigestion, and other affections of the nervous, circulatory and digestive organs."--W. H. Hammond, the eminent surgeon of New York city and formerly Surgeon General, U.S.A.

Drs. Seaver of Yale University and Hitchc.o.c.k of Amherst College, instructors of physical education in these two colleges, have clearly demonstrated by personal examination and recorded statistics that the use of tobacco among college students checks growth in weight, height, chest-girth, and, most of all, in lung capacity.

Additional Experiments.

Experiment 66. Test a portion of _C_ (Experiment 57) with solution of iodine; no blue color is obtained, as all the starch has disappeared, having been converted into a reducing sugar, or maltose.

Experiment 67. Make a thick starch paste; place some in test tubes, labeled _A_ and _B_. Keep _A_ for comparison, and to _B_ add saliva, and expose both to about 104 F. _A_ is unaffected, while _B_ soon becomes fluid --within two minutes--and loses its opalescence; this liquefaction is a process quite antecedent to the saccharifying process which follows.

Experiment 68. _To show the action of gastric juice on milk_. Mix two teaspoonfuls of fresh milk in a test tube with a few drops of neutral artificial gastric juice;[30] keep at about 100 F. In a short time the milk curdles, so that the tube can be inverted without the curd falling out. By and by _whey_ is squeezed out of the clot. The curdling of milk by the rennet ferment present in the gastric juice, is quite different from that produced by the "souring of milk," or by the precipitation of caseinogen by acids. Here the casein (carrying with it most of the fats) is precipitated in a neutral fluid.

Experiment 69. To the test tube in the preceding experiment, add two teaspoonfuls of dilute hydrochloric acid, and keep at 100 F. for two hours. The pepsin in the presence of the acid digests the casein, gradually dissolving it, forming a straw-colored fluid containing peptones. The peptonized milk has a peculiar odor and bitter taste.

Experiment 70. _To show the action of rennet on milk_. Place milk in a test tube, add a drop or two of commercial rennet, and place the tube in a water-bath at about 100 F. The milk becomes solid in a few minutes, forming a _curd_, and by and by the curd of casein contracts, and presses out a fluid,--the _whey_.

Experiment 71. Repeat the experiment, but previously boil the rennet. No such result is obtained as in the preceding experiment, because the rennet ferment is destroyed by heat.

Experiment 72. _To show the effect of the pancreatic ferment (trypsin) upon alb.u.minous matter_. Half fill three test tubes, _A, B, C_, with one-per-cent solution of sodium carbonate, and add 5 drops of liquor pancreaticus, or a few grains of Fairchild's extract of pancreas, in each. Boil _B_, and make _C_ acid with dilute hydrochloric acid.

Place in each tube an equal amount of well-washed fibrin, plug the tubes with absorbent cotton, and place all in a water-bath at about 100 F.

Experiment 73. Examine from time to time the three test tubes in the preceding experiment. At the end of one, two, or three hours, there is no change in _B_ and _C_, while in _A_ the fibrin is gradually being eroded, and finally disappears; but it does not swell up, and the solution at the same time becomes slightly turbid. After three hours, still no change is observable in _B_ and _C_.

Experiment 74. Filter _A_, and carefully neutralize the filtrate with very dilute hydrochloric or acetic acid, equal to a precipitate of alkali-alb.u.men. Filter off the precipitate, and on testing the filtrate, peptones are found. The intermediate bodies, the alb.u.moses, are not nearly so readily obtained from pancreatic as from gastric digests.

Experiment 75. Filter _B_ and _C_, and carefully neutralize the filtrates. They give no precipitate. No peptones are found.