183. These may be defined substances which are, in themselves, incapable of nourishing, but which, in concert with our food, promote its digestion, or correct some of its deleterious properties. The existence and necessity of such agents are far more universal and important than has been generally supposed1. The bitter principle which exists in the composition of grasses and other plants appears to be essential to the digestion of herbivorous animals; it acts as a natural stimulant; for it has been shown, by a variety of experiments, that it passes through the body without suffering any diminution in its quantity, or change in its nature. No cattle will thrive upon grasses which do not contain a portion of this vegetable principle: this fact has been most satisfactorily proved by the researches of Mr. Sinclair, gardener to the Duke of Bedford, which are recorded in that magnificent work, the "Hortus Graminetis Wobarnensis." They show, that if sheep are fed on yellow turnips, which contain little or no bitter principle, they instinctively seek for, and greedily devour, any provender which may contain it; and that if they cannot so obtain it, they become diseased, and die.

We are ourselves conscious of the invigorating effects of slight bitters upon our stomach; and their presence in malt liquors not only tends to diminish the noxious effects of such potations, by counteracting the indirect debility which they are liable to occasion, but even to render them, when taken in moderation, promoters of digestion. The custom of infusing bitter herbs in vinous drinks is very ancient and universal. The poculum absinthiatum was regarded in remote ages as a wholesome beverage, and the wormwood was, moreover, supposed to act as an antidote against intoxication. Civilization has, in a great measure, destroyed our natural taste for bitters; while, by improving our food, it has probably rendered its stimulus less necessary. The Swiss peasant cheers himself amid the frigid solitude of his glaciers with a spirit distilled from gentian, the extreme bitterness of which is relished with a glee that is quite unintelligible to a more cultivated taste. It may be safely affirmed, that the utility of this condiment is in an inverse ratio with the nutritive, or rather digestible power of a vegetable substance; and we accordingly find, in conformity with that universal scheme of self-adjustment and compensation, so visible in all the operations of nature, that cultivation, which exalts and extends the nutritive powers of vegetable bodies, generally diminishes their bitterness in the same proportion.

The natural history of the potatoe, already alluded to (5), offers a good illustration of this fact.

1 Pharmacologia, edition 8th, p. 111. Dr. Bostock observes that it is a curious fact, strikingly exemplified in the history of condiments, that such articles as are, in the first instance, disagreeable to the palate, are those for which we afterwards acquire the strongest partiality, and which even become necessary for our comfort; whereas the frequent repetition of flavours that are originally grateful is very apt to produce a sense of satiety, or even of disgust. The examples of tobacco, garlic, and even assafoetida, on the one hand, and of such substances as possess simple sweetness, on the other, may he adduced in proof of this position.

184. From the different nature of condiment, it has been usually divided into three classes; viz. the saline, the spicy, or aromatic, and the oily.