The experience of mankind has shown them that food unpleasing to the palate is apt to produce disgust or even vomiting, while palatable food is eaten with pleasure, retained with ease and digested with comfort. But it is only recently that the experiments of Pawlow have demonstrated scientifically that appetizing food, even when it simply passes through the oesophagus without entering the stomach, excites the secretion of gastric and pancreatic juices as well as that of saliva, so that a food which per se is less digestible than another may be more readily digested if it is more palatable. In accordance with their experience men have everywhere tried to render tasteless and unappetizing food more palatable by the addition of savoury substances. Thus the Hindoo eats curry along with his insipid rice and the Spaniard eats onions with his bread.
Even when food is already palatable, its taste is heightened by the Englishman who takes mustard with his beef, red currant jelly with his roast mutton or venison, caper sauce with boiled mutton, and apple sauce with roast pork, duck, or goose. It is curious to note that even in condiments there is a tendency to bring about the proper relation between the various kinds of nutriment. Thus onions and strong tasting cheese are not only powerful flavouring matters but they contain a large amount of nitrogen and are thus most useful adjuncts to a dietary of which bread forms a large portion. Fried bacon, herrings, sardines, etc., not only render potatoes or bread more palatable, and butter sauce gives a richer flavour to boiled fish, but they supply the fat which would be deficient in these articles of diet. Red currant jelly supplies the carbo-hydrate which is deficient in the mutton, and the apple sauce seems to counteract the excess of fat in pork, duck, or goose. It would almost seem, too, as if vegetable acids were useful in the digestion of fat because the Italian peasantry who live much upon bread and oil drink sour wine along with them. The palatability of food is not to be regarded as a mere question of gratifying the sense of taste and thus affording pleasure, which some people are apt to look upon as being in its nature sensual and debased. It is a matter of every-day observation that appetizing food, or even the idea of it, is sufficient to make the mouth water, that is to increase the flow of saliva. Saliva is not only a powerful digestive of starchy matters but it tends to stimulate the secretion of gastric juice, and this acts in its turn as a stimulant to the intestine when the gastric juice enters the duodenum and a body is produced in its mucous membrane to which the name of secretin has been given by its discoverers, Bayliss and Starling. This is absorbed and carried by the blood to the pancreas, to which it acts as a stimulant and causes it to secrete an active digestive juice. The activity of the pancreas may, as will be mentioned hereafter, increase the metabolism in the muscles and thus food which from its composition ought to be readily digested, may, if unappetizing, be of very much less nutritive value than other food less easily digestible in itself but pleasing to the palate.
It may be objected that hot buttered toast, which is very palatable, is often found to be indigestible while crisp toast on which butter is spread may be digested with ease. The probable reason of this is that the hot buttered toast is soft and is swallowed without much mastication, while the crisp toast must be well chewed before it can be swallowed. There may possibly be another reason also, viz. that the butter which is spread on the crisp toast becomes more completely subdivided into minute particles, and thus is more easily digested, while the melted butter of the buttered toast runs together more readily into oily masses in the stomach and thus becomes indigestible. When fat is overheated irritating products are apt to be formed from it such as acrolein, which causes the disagreeable smell from a badly extinguished candle. In cooking pastry some such decomposition occasionally occurs and symptoms of irritant poisoning may occur from eating it. Inferior qualities of butter which have such a strong and disagreeable flavour that they cannot be eaten in the usual way are sometimes used under the name of cooking butter to make pastry, and such butter, although not detected by the palate in pastry, may give rise to sickness and vomiting. On account of such liabilities to cause illness pastry has a bad name, but from my own experience I am inclined to think that pastry, if well made and from the best materials, is wholesome and digestible.
Pawlow's demonstration that savoury food, in the mouth, or even when simply showed to an animal without being eaten at all, will excite the secretion of all the digestive juices explains why the Irish peasantry in time of famine when they were compelled to live on potatoes alone hung up a red herring and pointed their potato at it so as to obtain the suggestion of savoury food. This is probably also the reason why cheese savouries and fruit are eaten at the end of a large dinner which by its amount might overtax the digestive powers of the individual if the digestive secretions did not receive an additional stimulus.
Another function of condiments is to relieve the flatulent distension which often occurs from fermentation in the intestine, especially when large quantities of hydro-carbons are consumed. The substances employed for this purpose are chiefly derived from the natural orders Labiatae and Umbelliferae, especially the latter. Thus we find that it is the custom to sprinkle caraway seeds upon cakes and to use fennel, dill and garlic both as a relish and to relieve distension.