Dolæus upon the cure of the gout by milk-diet / To which is prefixed, an essay upon diet

by Johann Doläus; William Stephens

Vegetables receive their Food from the Air and Earth, by means of several Recipient Vessels placed in the Root and Bark, (analogous to the Lacteals in Animals) conveyed and diluted by a sufficient Quantity of Water: This Food thus received, which I shall beg Leave to call Vegetable Chyle, is digested and assimilated in the Course of Circulation, through the Vessels of the Plant, till it is converted into Vegetable Substance, and is formed into the several differing Vegetable Juices, Gums, and Resins, that are peculiar to each Species of Plants. The Remainder, after the proper Separations, is evaporated thro’ the Pores of the Skin and through the Leaves, in the Manner of Animal Transpiration. I content myself here with this short Hint of Vegetable Nutrition, because I have treated it more at large and expresly in another Place: It is more material at present to examine the several Juices which circulate in the Vessels of Vegetables, because, in regard to Diet, they will appear to be the Matter of Animal Nutrition; for the Vessels of Plants are no other than meer Earth bound or connected together with Oyl, by the Means of some very powerful Attraction: This Earth is undissoluble by the utmost Force of Fire, since after burning a Plant in the open Fire, we find it left entire.

The Chyle of Plants seems to be made up of whatever Parts in the Earth are soluble in Water, so as to be capable of being received into the Absorbent or Recipient Vessels of Plants, before taken Notice of; and consequently may consist of Salts, Oyls, Fumes of Minerals, Metals, and other fossil Bodies, the putrified Parts of Animals and Vegetables. In its first State it is, to be sure, very crude; but by the Structure and Fabrick of the Plant, and the various Vessels it is strained thro’, it is changed, elaborated, secreted, and assimilated into the Substance of the Plant; whence it follows, that in Vegetables are contained Salts, Oyl, Water, and Earth, and probably Metals too, for the Ashes of Vegetables yield somewhat which the Load-Stone attracts.

This Juice, when it first enters the Root, is Earthy, Watry, Poor, and Acid, it is in the Form of a fine and subtle Water; the nearer it is to the Root, the more it retains of its proper Nature, the further it is from the Root, and the more Action it hath sustained it approaches nearer to a Vegetable Nature, as will appear by pursuing it a little further. In the Trunk and Branches it is further prepared, tho’ even here it is Watry and Acid, as appears by tapping Trees at the proper Season: It is more concocted in the Bud, where the Leaves coming to be unfolded, serve as Lungs for the further Preparation of it in the Course of Circulation; in the Flower, Leaves and Parts of Generation, it is still further elaborated, and becomes in its utmost Perfection, fine enough to preserve and nourish the Embryo in the Seeds of Plants. This Nutritious Juice or Chyle is pretty universal, and is found in every Part of a Plant, but more or less in Quantity, and more or less impregnated with the more Elaborate Juices, according to the Number and Degree of its Circulations. It seems to be the universal Diluent and Conveyer of other and more elaborated Particles. Besides what I have mentioned, there are Juices particular to particular Parts of Plants; as Oyl, Wax, and Manna to the Leaves; Volatile Oyl or Spirit, and Honey to the Flower; a very fine Essential Oyl or Balm to the Seed, and that in great Quantity; Oyl, Balm, Pitch, Resin and Gum to the Bark: Besides which, there is a Juice peculiar to each Plant, and received in Vessels of its own, in which a good Deal of its Specifick Nature may consist, (for it is not reducible to any of those before mentioned) most of the English Authors call this the proper Juice of the Plant, but Boerhave and later Writers call it the Blood. I should digress too much to enter into the natural History of these several Parts of Vegetables; my Design at present reaching no further than with Respect to their Assimilation into Animal Substance; and therefore I refer to the Authors who have expresly treated of these Matters, and proceed to examine Vegetable Juices in another Light.

The Juices of Plants are Watry, Saline, Oily, Spirituous, Gummy, Balsamick, or Resinous, all discoverable by Art. The Water is generally found in the Absorbent Vessels of Plants, but mixed with a Proportion of Salt, which, tho’ always soluble in Water, otherwise appears of very different Nature in different Plants, and differs in Degree of Volatility.

The Oily Part is that which grows Fluid at the Fire, proves inflammable, and will not unite with Water, without the Intervention of Salt. It is seldom obtained pure from Vegetables, because therein it exerts so very strong an attractive Force upon Salt, Water, and Earth, that nothing less than the Force of Fire, assisted by the Action of the Air, can separate them, as appears in Helmont’s Everlasting Coal.

The Spirituous Parts of Plants, or those which contain the Odour and Taste, are very volatile, will mix with Water, and sometimes burn in the Fire, the Oyl of the Vegetable being here greatly attenuated, broke, and subtilized; as appears by its being exhalable by the Heat of the Summer Sun, so as to form the particular Atmosphere of the Plant, and fill the Air with Particles that affect our Senses even at some Distance.

Gums are such Productions of Vegetables, as will mix with Water, dissolve over the Fire, and burn away, being tough viscid Substances, and contain a large Proportion of the Oyl and Salt of the Plant. Balsams are native Oyl of Vegetables, brought to a thick Consistence, but containing a large Proportion of an acid Spirit and Salt: However, they differ greatly from the Oyls they afford. Lastly, Resins are such Productions of Vegetables, as being hard and dry, prove brittle in the Cold, soluble by Heat, inflammable and misceable with Oyl, but not with Water.

It would be endless to give an Account of the particular Qualities of the proper Juices of Plants; since these differ in different Plants, and many Times in different Parts of the same Plant. There is a much greater Variety in Vegetable than in Animal Nature; and a much greater Difference in the Juices of one than of the other; for the Number of different Plants known and used very much exceeds the Number of different Animals known and used; and particular Plants have greater Variety of Juices than particular Animals; whose Juices (if I may so speak) are more homogenial than those of Plants. This will appear more evidently by comparing what hath been here said, with the Consideration of Animal Substances with Regard to Diet.

I have hitherto considered Vegetables in their natural State, but before we can apply what hath been laid down to Animal Diet, we must consider some Changes many of them undergo, before they are used. The Chief of these happens by Fermentation, the Effects of which upon Vegetables deserve to be considered; since Bread, Wine, and Malt Liquors, so great a Part of our common Food, are prepared from Vegetables that have gone thro’ this Operation, or are mixed with Ferments in their Preparation.