The common Effects of the Art of Cookery upon Vegetables, will be understood by what happens in the Decoction of Plants. In boiling any Plant, its most sublime fluid Part flies off, and indeed it is incapable of bearing a greater Heat than that of the Summer Sun, the Salts of the Plant are dissolved in the Water, and its thicker and grosser Oyl rises to the Top, like a fat Scum; so long as the Plant retains any Taste or Odour, change the Water as often as you please, there will constantly arise a fat, odorous, viscous, inflammable and frothy Matter, which can be no other than the Oyl of the Plant loosened from the Salts. In Proportion then, as the Salts are dissolved in the boiling Water, the Oyl attenuated, as it must be before it can be so far specifically lighter as to arise to the Top, we are to judge how far the Art of Cookery is serviceable in the Preparation of vegetable Diet.
From what was said before in relation to Fermentation, it is plain that the vegetable Oyls are much volatilized, rendred more active, and separated from the Salts; upon this Account it is, that they are endowed with an inebriating Quality, which is confined entirely to Wines, for no other Substance hath that Quality. No one was ever drunk with eating Grapes, or drinking Must or Wort before Fermentation. The stupifying Quality of Poppy, Henbane, Mandrakes, Nightshade, and other Plants of that Class, is very different from the Effects of Wine or its Spirit. The chief Effect of Fermentation, in Regard to Diet, is supposed to consist in rendring vegetable Substance less difficult to be overcome by the Action of animal Organs and Mixtures, and easier to the digestive Powers; but there are other good Effects not so commonly thought of; fermented vegetable Substance is very little subject to Putrefaction, and is a great Preservative against it. By the styptick Power that the Spirit is endowed with, the Tone of the Fibres is increased in Digestion, their Force enlarged, and consequently their Action greater upon the vegetable Parts, and a larger Quantity of animal Juices mixed with them; and it is no difficult Matter to imagine, that the inward Heat of an human Body should draw forth the Spirit of fermented Liquors.
The Parts of Vegetables most used in Food, are the Seeds of Plants, our common Bread and Drink being made from them: These, by what was said before, contain the most elaborated Juices, the greatest Quantity of fine Oyl and Spirit, and are consequently most fit for Nourishment; several Fruits are eaten Raw, because their Juices are concocted to the utmost Degree of Perfection, and contain, in greatest Quantity, the finest and most elaborated vegetable Oyl, mixed with the essential Salts peculiar to each, which would be lost in Decoction: But the coarser Parts of Vegetables, as Roots, Leaves, Stalks, unripe Fruits, and Flowers, require the Arts of Cookery to be exercised upon them, to render them more easily subject to the animal Powers, and assimilable to their Juices.
I design not to enter into the several specifick Differences of Vegetables, I hope I have said enough to explain their general Nature, and how they become reducible into animal Substances; I shall next consider these Substances in the same Manner.
By all the Tryals yet made upon animal Substances, they are resoluble into the same Parts with Vegetables, only differently modified; that is, as we saw before, Water, Earth, Salt and Oyl, the specifick Spirit being no other than Water impregnated with the specifick and highest rectified Oyl and Salt, the Water and Earth in both are individually the same; and though there be good Reason to imagine, that there is originally but one Oyl in Nature, and that the fixt Salt of Vegetables, and the volatile Salt of Animals, may be originally the same, since transmutable into one another; yet it is necessary to examine these two Principles in animal Substances, that by comparing them with what we before discovered in Vegetables, we may have some Notion of their Differences with Regard to their Use in Diet.
The great Excess of animal Heat and Motion, beyond what is necessary to Vegetables, the stronger and quicker Circulation of their Juices, necessarily require and occasion that the Oyls and Salts in animal Bodies should be differently modified from what they are in Vegetables. No Motion is performed in Animals without some Portion of Oyl, and perhaps Water too, to lubricate the Parts, and keep them supple; the Attrition would cause great Mischief, make the Motion uneasy, wear away and burn up the Parts, if they were not softned and moistned by an oily Fluid; and accordingly we find all the Muscles, Tendons, Joints and other Parts employ’d in Motion, to have Repositories of this Oyl placed about them, and that so artificially, that the Very Motion occasions the Diffusion of this Oyl upon them. There is an innate Principle of Heat or Fire, that attends the vital Powers, that may very well occasion the Change and Volatilization of Salts in animal Substances, in the same Manner as was before observed in the Putrefaction of Vegetables.
Animal Oyls differ according to the Principles inherent in them, for when freed from Earth and Salts (which is very difficult by Reason of their mutual Attractions under certain Circumstances) they appear to be simple and unactive, and the same in all animal Bodies.
By this Account then we are principally to regard the different Quantities and Degree of Volatility in these Salts, and the Degree of Consistence or Impregnation of animal Oyls with them. It must be observed, that the Salts in the Bodies of living Animals are not perfectly the same they appear to be, when extracted thence by chymical Resolutions; a great Alteration is made by the Fire, and a good deal by the Tendency all animal Substances have to Putrefaction, upon a Stagnation of their fluid Parts: Even in the Evaporation of human Blood (fresh drawn) by a gentle Fire, this Salt, though not perfectly fixed, will not rise, but only the Spirit: These Salts are of a mild attenuating Nature in healthy Bodies, whose vital Powers are sufficient to subdue the Substances they feed upon: But in such as have not that vital Power in that Degree, or commit Errors in Diet, where these Salts are not sufficiently attenuated, or the first Digestion stronger than the concoctive Powers or the Discharges, these Salts acquire Properties productive of many acute and chronical Diseases; (not within the Compass of this Enquiry) these may be prevented, and sometimes cured, by a strict Application to Diet, proper to correct the different Modifications of these Oyls and Salts.
I own it is pretty Difficult to determine the exact Degree of Volatility these Salts acquire in any particular Animal, or in different Parts of the same Animal; yet there are very evident Marks of a Defect, or Exceeding in the Volatility of these Salts, by examining the Discharges from Animals, by a greater or less Tendency to Putrefaction, by several Distempers more especially incident to human Bodies, and other Methods of Art to be met with in the History of Physick.
From what was said before, it is evident that an Animal, whose Juices are supplied from animal Juices, hath a more alkalescent Tendency than an Animal supplied with vegetable Juices; that is, the Salts are more highly volatilized, and impregnate the Oyls, Water, and other Fluids in a stronger Manner, and in greater Quantities; and in Fact, we find the Substance of such animal Bodies, as are fed upon Animals, or Use stronger Exercise, are more liable to Putrefaction, than the Substance of Animals that feed upon Vegetables, and are more slothful. Fish, Foxes, Hawks, Venison, Horses, have their Substance more liable to Putrefaction, and discover to our Senses more exalted Salts and Oyls, than tame Fowl, Sheep, and Oxen; the Juices of poisonous Animals have them still more exalted, as in the Viper.