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the fun or the north wind, are reckoned by Theophraftus to produce the beft and pureft tar: And the Idasan pines were diftinguifhed from thofe growing on the plain, as yielding a thinner, fweeter, and better fcented tar, all which differences I think I have obferved, between the tar that comes from Norway, and that which comes from low and ^warnpy countries.
29. Agreeably to the old obfervation of the Peripatetics, that heat gathereth homogeneous things and difperfeth fuch as are heterogeneous, we find chemiftry is fitted for the analyfis of bodies. But the chemiftry of nature is much more perfect than that of human art, inafmuch as it joineth to the power of heat that of the moft exquifite mechanifm. Thofe who have examined the ftructure of trees and plants by micro'fcopes, have difcovered an admirable variety of fine capillary tubes and veflcls, fitted for feveral purpofes, as the imbibing or attracting ef proper nourifhment, the diftributing thereof through ail parts of the vegetable, the difcharge of fuperfiuities, the fecretion of particular juices. They are found to have ducts anfwering to the trachese in animals, for the conveying of air; they' have others anfwering to lacteals, arteries, and veins. They feed, digeft, refpire, perfpire and generate their kind, and are provided with organs nicely fitted for all thofe ufes.
30. The fap veflels are obferved to be fine rubes running up through the trunk from the root. Secretory veflels are found in the bark, buds, leaves, and flowers. Exhaling vefTels for carryin" off excrementitious parts, are difcovered throughout the whole furface of the vegetable. And (though this point be not fo well agreed) doctor Grew in his Anatomy of plants, thinks there appears
circulation of the fap, moving downwards in the root, and feeding the trunk upwards.
31. Some difference indeed there is between Jearned men, concerning the proper ufe of certain parts of vegetables. But whether the difcoverers have rightly guefled at all their ufcs or no, thus much is certain, that there are innumerable fine and curious parts in a vegetable body, and a wonderful fimilitudeor analogy between the mechanilrn of plants and animals. And perhaps fome will think it not unreafonable to fuppofe the mechanilm of plants more curious than even that of animals, if we confider not only the feveral juices fecreted by different parts of the fame plant, but alfo, the endlefs variety of pices drawn and formed out of the fame foil, by various fpecies of vegetables; which mult therefore differ in an endlefs variety, as to the texture of their abforbent veflels and fecretory duels.
32. A body, therefore, either animal or vegetable, may be confidered as an organifed fyftem of tubes and veflels, containing feveral forts of fluids. And as fluids are moved through the veflels of animal bodies, by the fyftole and diaitole of the heart, the alternate expanfion and condenfation of the air, and the ofcillutions in the membranes and tunicks of the vefiTds; even fo by means of air expanded and contracted in the trachese or veflels made up of elaftic fibres, the fap is propelled through the arterial tubes of a plant, and the vegetable juices, as they are rarefied by heat or condenfed by cold, will either afcend and evaporate into air, or defcend in the form of a grofs liquor.
33. Juices therefore, firft purified by ftraining through the fine pores of the root, are afterwards exalted by the action of the air and th« veflels of the plant, but, above all, by the action of the fun's
light; which at the fame time that it heats, doth wonderfully rarefy and raife the fap; till it perfpires and forms an atmofphere, like the effluvia of animal bodies. And though the leaves are fuppof«d. to perform principally the office of lungs, breathing out excrementitious vapours, and drawing in alimentary; yet it feems probable, that the reciprocal aft ions of repulfion and attraction are performed alJ over the furface of vegetables, as well as animals. In which reciprocation, Hippoerates fuppofeth the manner of nature's acting, for the nourifhment and health of animal bodies, chiefly toconfift. And, indeed, what (hare of a plant's nourifhment is drawn through the leaves and bark, from that ambient heterogeneous fluid called air, is not eafy to fay. It feems very confiderable and altogether neceflary, as well to vegetable as animal life.
34. It is an opinion received by many, that the fap circulates in plants as the blood in animals: that it afcends through capillary arteries in the trunk, into which arc inofculated other veflels of the bark anfwering to veins, which bring back to the root the remainder of the fap, over and above what had been depofited, during it's afcent by the arterial veflcls, and fecreted for the feveral ufes of the vegetable throughout all it's parts, Item, branches, leaves, flowers, and fruit. Others deny this circulation, and affirm that the fap doth noc return through the bark vefTels. It is neverthelefs agre«d by all, that there are afcending and defcendtng juices; while forne will have the afcent and defcent to be a circulation of the fame juices through, different veffels: others will have the afcending juice to be one fore attrufted by the root, and the defcending another imbibed hv the leaves, or extremities of the branches: I.iftly, others think that
the fame juice, as it is rarefied or condenfed by heat or cold, rifes and fubfides in the fame tube. I fhall not take upon me to decide this controverfy. Only I cannot help obferving, that the vulgar argument from analogy between plants and animals lofeth much of ii's force, if it be confidered, that the fuppofed circulating of the fap, from the root or lacteals through the arteries, and thence returning, by inofculations, through the veins or bark veflels to the root or lacteals again, is in no fort conformable or analogous to the circulation of the blood.
35. It is fufficient to obferve, what all muft acknowledge, that a plant or tree is a very nice and complicated machine (a); by the feveral parts and motions whereof, the crude juices admitted through the abforbent veflels, whether of the root, trunk, or branches, are varioufly mixed, feparated, altered, digefted, and exalted in a very wonderful manner. The juice as it paffeth in and our, up and down, through tubes of different textures, fhapes, and fizes, and is affected by the alternate compreffion and expanfion of elaftic veflels, by the viciflitudes of feafons, the changes of weather, and the various action of the folar light, grows ftill more and more elaborate.
36. There is therefore no chemiftry like that of •nature, which addeth to the force of fire, the moft delicate, various, and artificial percolation (b). The inceflant action of the fun upon the elements of air, earth, and water, and on all forts of mixed bodies, animal, vegetable and foffil, is fuppofed to perform all forts of chemical operations. Whence it fhould follow, that the air contains all forts of chemic productions, the vapours, fumes, oils, falts,
(a 30, 3>- 0) 29
and fpirits of all the bodies we know: from which general aggregate or mafs, thofe that are proper being drawn in, through the fine veffcls of the leaves, branches, and Item of the tree, undergo in it's various organs, new alterations, fecretions,' and digettions, till fuch time as they afiume tha moft elaborate form.
37. Nor is it to be wondered, that the peculiar texture of each plant or tree, co-operating with the Iblar fire and pre-exifting juices, fhould fo alter the fine nourifhment drawn from earth and air (a), as to produce various fpecific qualities of great efficacy in medicine: especially if it be confidered that in the opinion of learned men, there is an influ* ence on plants derived from the fun, befides it's mere heat. Certainly doctor Grew, that curious anatomift of plants, holds the folar influence to differ from that of a mere culinary fire, otherwife than by being only a more temperate and equal heat.
38. The alimentary juice taken into the lacteals, if I may fo fay, of animals or vegetables, confifts of oily, aqueous, and faline particles, which beingdiffolved, volatilifed, and diverfly agitated, part thereof is fpent and exhaled into the air; and that part which remains is by the ceconomy of the plant, and action of the fun, ftrained, purified, concected, and ripened into an infpifiated oil or balfam, and depofued in certain cells placed chiefly in the bark, which is thought to anfwer the panniculus adipofus in animals, defending trees from the weather, and, when in fufficient quantity, rendering them evergreen. This balfam, weeping or fweating through the bark, hardens into refin ; and this rrioft copioufly in the feveral fpecies of pines and
C 2 firs,