Popular Science Monthly/Volume 1/October 1872/Physiological Influence of Condiments
| PHYSIOLOGICAL INFLUENCE OF CONDIMENTS. |
By Prof. VOIT.
(ABSTRACT OF VOIT'S REPORT, BY ANDRÉ SANSON.)
BESIDES the elements of nutrition which we consume at every meal, there is also a number of other elements which serve to make the food savory and appetizing. These latter do not strictly come within the definition of nutritive substances, and are properly denominated condiments. Though not in themselves nutritious, the condiments are nevertheless necessary to nutrition. Their importance, however, as constituents of food, has not hitherto been duly appreciated. We must determine with exactitude the action both of the various elements of nutrition and of the condiments, and employ, to express this difference, well-defined terms, if we would avoid all confusion in treating the subject. Before we state what is the action of the salts and of the extractive elements of nutrition, as condiments, we must first consider the action of condiments in general. It is commonly supposed that they excite in the palate agreeable sensations, and so produce simply an excitation which, however, serves no useful purpose; and that, when once they enter into the blood, they bring about in it abnormal states and unnatural excitation. However, they are not regarded as hurtful.
Condiments act principally upon the nervous system. Some of them, for instance, excite the nerve termini of the mucous membrane of the digestive canal, whence the excitation or stimulus passes to certain centres in the intestine, or to more remote centres in the spinal cord, the brain, etc. Others of them, having been absorbed in the blood, reach the central organ of the nervous system, and act upon it. Passing beyond all these nerve-centres, their influence may extend farther, and may, through the intestinal canal, affect portions of the system which have no direct relation to digestion.
Bearing all this in mind, we perceive that the term condiment is commonly used in too restrictive a sense, being applied to but a few of the substances which act upon the system in the manner above indicated. There is no reason why we should give the name of condiments only to those substances which produce agreeable and useful stimulation in the nervous system, either by exciting the palate or by entering: into the blood. The site of the excitation is immaterial, and cannot determine whether a substance is or is not properly a condiment. The first effects produced by sundry agents not commonly regarded as condiments—tea and coffee, for example—are at bottom the same as those produced by the condiments. As for those substances which produce their effects only when they have entered into the blood, and which have nothing to do with digestion, these have been regarded as condiments if they are absorbed by the intestinal canal, as caffeine; or by the nasal mucous membrane, as the nicotine of snuff. To be consistent, we must give the same name of condiment to sundry substances which are not at all eaten. This will readily be admitted with regard to the sense of smell, since many dishes, instead of pleasing by their flavor, please rather by their agreeable odor. The volatile elements of food, by gratifying the sense of smell, become true condiments. The same is to be said of other volatile elements which are not derived from articles of food, such as the fragrance of flowers, etc.
The excitation of the organs of taste or of smelling produces, in certain determinate portions of the brain, corresponding agreeable sensations. The process is essentially the same in the case of sensations of hearing or of seeing. Hence we might reckon among condiments the vibrations of the ether, and those of sound. However wide the difference between the pleasure we experience in the contemplation of a Madonna by Raffaelle, the hearing of one of Beethoven's symphonies, inhaling the fragrance of a rose, and tasting a savory fruit, still these have all something in common. External causes will always produce a movement in the nerves, and this will be transmitted to certain points of the central organ, where it will give rise to sensations; and thence again there may be transmitted to still other centres other nerve-influences, which will produce simultaneous action in other points.
The term condiment, as commonly used, is taken in too restricted a sense in another point of view. An agent acting upon the mucous membrane of the mouth, stomach, or intestine, may produce in the nervous system important effects as regards digestion, and yet we may have no sensation of this either through taste or through smell, its parts not entering into communication with the central organ of sensation.
Having thus given a notion of what he understands by condiments, the author lays some stress upon the foregoing considerations, in order to show that a substance may be rigorously denominated a condiment, without exercising any agreeable effect upon the organs of taste. Still the chief condiments do undoubtedly produce this effect. A mixture of pure albumen, fat, starch, salts, and water, would suffice for alimentation, and yet it would be a satisfactory ration only in case of extreme want. In any other case we should regard it as unpalatable, and should refuse to partake of it. All alimentary substances, even those which come from the vegetable kingdom, are combined with substances which, though not nutritious, still have a flavor, and the former are not easily digested unless they first gratify the palate. Substances without flavor, or which are repulsive to the palate, are nauseating, and cause vomiting. There exists, therefore, a functional relation between the central organ of taste and the stomach. If the former acts upon the latter adversely, it may also act favorably upon it. In like manner, too, the central organ of taste is influenced by the stomach. Satiety deprives food, which once was agreeable to us, of its power of gratifying the palate.
Several condiments act upon the stomach, or on the intestine, after having first produced an agreeable sensation of taste. The excitation to which they give rise does not extend to the central organ, there to produce the same sensation. They are limited to the stomach and to the intestine, and serve to favor digestion and absorption. The gastric juice, we know, is not secreted continually, but only when there is something in the stomach. When the mucous membrane of that organ is excited by the contact of a quill, for instance, or of a glass rod, the gastric juice begins to flow, and the vessels of the mucous membrane become charged with blood. The presence of food produces the same effect. But there are other excitations which appear to act even more powerfully on the stomach. If we introduce a drop of alcohol or ether, or a solution of common salt, into the stomach of a living animal, the juice will flow from the glands, just as the same effect is produced by the thought of some savory dish. We may observe this when we offer a hungry dog a piece of meat. It is for this reason that we frequently add to our food substances strongly salted or aromatized, as, for instance, a caviare, or a glass of some spirituous liquor, such as sherry. The same effect may even be produced by the very sight of the label borne by such articles. When meat is roasted at a hot fire, it brings about this same result in the best and simplest manner; and most of the flavors and pleasing odors of food have the same effect. Hence we see their importance as means of promoting digestion.
The extract of meat belongs to the class of condiments. It first gratifies the palate, and then produces important results in the stomach. This is not due to the nutritive salts it contains, nor to any special effect it produces on absorption or nutrition. If an animal gets for food only extract of meat, it will succumb more quickly than if no food at all were given, as was demonstrated by Kemmerich in the case of a dog. We may account for this either on the supposition that the salts accelerate the transformation of albumen, or that the potash of the extract acts injuriously on the heart. Therefore, when vessels, fortresses, armies, and hospitals, are supplied with this meat-extract, they obtain what we must regard as an excellent condiment; but that will not supply the place of a single grain of the nutritive elements; and in this regard it is analogous to table-salt, coffee, tobacco, etc. Nevertheless, we cannot question the beneficial effect of a good meat-broth upon the stomach, whether in health or in sickness. Especially does it produce a good effect in the case of convalescents whose stomach is in a chronic state of debility. They cannot retain common food, except it is given to them in the shape of broth. Just as the excitation of the mucous membrane of the mouth has an effect upon the stomach, so, probably, the stomach acts upon the intestine. Thus, for instance, soon after the stomach is filled, we find the pancreas addressing itself to its function.
There are some condiments the effects of which are not at first local. They act only after having been absorbed, and their action is then perceptible in the central nervous system. This is the case, for instance, with coffee, tea, tobacco, alcoholic drinks, etc., the general action of which is well known. It has been supposed that we have here an arrest of decomposition, an economy of nutritive material. In fact, we have only another mode of arrangement or of change in the inward phenomena. The amount of work of which a man is capable depends very much upon his momentary disposition. With equal nutritive transformations, and with equal production of living force, the man who undertakes a work under favorable moral conditions will perform it more easily than another who happens to be oppressed and weighed down by some affliction. A stroke of the whip causes a horse to surmount an obstacle, before which he would have stood still without that stimulus; and yet the latter does not communicate to him any force; it only induces him to exert the force he already possessed. It is thus that condiments act upon certain determinate parts of our nervous centre, and so enable us to attain our ends. We may regard as of similar nature to this the action of opium or of musk, under the influence of which a man, who before was perfectly powerless, appears to get new life, without any demonstrable elementary change having taken place in his body. The same is to be said of the influence of alcohol, and of common salt, leaving out of the account their local action in the mouth and stomach.
Does the same hold good for extract of meat? None of the known organic elements of this extract have an action analogous to that of caffeine, nicotine, or alcohol. Still it is certain that the potash which it contains brings about results which are essentially general. It renders the nerves and the muscles more excitable, and produces an acceleration of the contractions of the heart. Kemmerich was at first disposed to attribute the exciting and quickening action of the extract to the potash which it contains; and he has shown that meat-extract, reduced to ashes, produces a fatal effect when administered in the same quantity which is fatal before it is so reduced. He has demonstrated that a dose of chloride of potassium, containing the same quantity of potash which is contained in a half-pound of meat, accelerates the beating of the heart in a healthy subject. Yet, notwithstanding this, we are not to overlook local action, and suppose with Kemmerich that the extract of meat might give place to a small quantity of potash, and still leave the food equally nutritious.
We might accordingly attribute to the extract of meat the same property which characterizes animal food, viz., the production of an extraordinary degree of energy and vigor. Here Voit observes that this property does not belong to the extractive elements, but rather to the albuminoid materials, the proportion of which contained in animal food exceeds that contained in vegetables, as compared with the non-nitrogenized elements. Indeed, if we feed a carnivorous animal on a small quantity of meat, with a large amount of fat and meat-extract, he loses his natural liveliness. The same theory holds good for man, when fed on vegetable diet and the extract of meat. His vigor is far less than when meat forms the basis of his food. But on the other hand, if we give to an herbivorous animal food rich in albuminoid principles, if, for instance, we give to a horse an abundance of oats, the result will be the same as when a carnivorous animal is given animal food.
The action of meat-extract on the animal economy is, therefore, simply that of a condiment. Liebig attributes to it no other action, though the matter has frequently been involved in confusion. This action is, however, very important and beneficial. It is also possessed by certain vegetable extracts. Thus soups of high flavor and very strengthening may be made with the extract of the tomato, which has an acid reaction.
The foregoing remarks give only a partial view of the important function of condiments in promoting nutrition. Neither man nor animals take their food without some condiment. The simplest food always possesses some quality which serves as its condiment. It is only in virtue of this that vegetables gratify the palate. Thus in fruits for example, there are acids, volatile oils, etc. Most of the condiments are derived from the vegetable kingdom. Every people has its own favorite condiment. Every one likes to find an agreeable flavor in his food, and we have it prepared in such a way as to acquire the peculiar flavor we like. For the same reason we like variety in articles of food. In time the persistent impression of one flavor produces disgust, and so what once was savory now becomes unpleasant. Therefore, if one were to be confined for a considerable time to a fixed diet, he would not thrive upon it, no matter how rich it might be in the elements of nutrition, for the reason that the influence of the condiment would be nullified.
There are, besides, many other influences which act upon digestion, but of which we commonly think little. In taking food we strive to combine various enjoyments, so that many organic manifestations may conspire together to promote the action of the digestive apparatus. The organ of smell is situated near that of taste. Those dishes which contain volatile elements are rather smelt than tasted. "We give an agreeable smell to some articles of food by adding to them others which are fragrant. Dishes to which we are unaccustomed we partake of with repugnance, and generally they cannot be retained. We also give to dishes agreeable forms, and set them on the table with some regard to their appearance, and this makes them "appetizing." If they are served up without any regard to such considerations, they excite only repugnance. The frame of mind in which one may happen to be is also a matter of importance. If our thoughts are preëngaged, or if we are in trouble, we have no desire for food. The presence of a sprightly child, or of friends, at the board, is a true condiment. How different is the process of digestion when a meal is taken in full view of a pleasing landscape, or behind the bars of a prison-cell!
We are continually exposed to a multitude of excitations or influences from without. These give us sensations which are not alone agreeable, but also useful and necessary. Thus alone can we live. Though by many persons the limits of moderation are overstepped in seeking this kind of gratification, and they are made thus hurtful, it does not thence follow that they are to be avoided. If some men make an abusive use of food, we are not therefore to conclude that the proper course is to abstain altogether from food, any more than we should conclude, from the fact that the feasts of Lucullus are every day repeated, that therefore, instead of palatable food, whether animal or vegetable, one should eat only a tasteless mixture of albuminates, fat, starch, etc. There is danger of excess in every action we perform, but a man of sense will always respect the law which determines for him what is beneficial and what hurtful.—Revue Scientifique.