This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Manna Pharm. Lond. & Edinb. Manna Jen Ros calabrinus Pharm. Paris. Manna: a sweet juice obtained from certain ash trees (a) in the southern parts of Europe, particularly in Calabria and Sicily, exuding from the leaves, branches, or trunk of the tree, and either naturally concreted, or exsiccated and purified by art.
* There are three ways in which manna is collected in Calabria. From the middle of June to the end of July, a very clear liquor exudes spontaneously from the trunk and branches of the tree, which by the fun's heat concretes into whitish masses, which are scraped off the next morning with wooden knives, and dried in the fun. This is called Manna in the tear. At the beginning of August, when this ceases to flow, the peasants make incisions in the bark, whence a juice flows, which concretes in larger masses and of a redder colour. This is the sat or common Manna. Besides these sorts, a third is procured by receiving the spontaneous exudations in June and July on straws or chips of wood fattened to the tree. This is the cannu-lated ox flaky Manna, and is accounted the finest of the three.
Juices of the same nature are collected, in the eastern countries, from other trees and shrubs (b): and similar exudations are some-times found on different kinds of trees in Eu-rope, as particularly on the larch in the Brianconois in Dauphiny. How far the manna juices of different vegetables differ from one another, is not well known: but thus much is certain, that one and the same tree affords mannas very considerably different, in their colour, in their taste, and in their disposition to assume a solid concrete form; that is, in their purity, or the greater or less admixture of oily or resinous matter.
(a) Fraxinus rotundiore folio; & Fraxinus humilior minore & tenuiore folio C. B. Fraxinus Ornus Linn.
(b) Vide Clufii exotic. lib. i. p. 164. Rauwolf itin. p. 74. Teixeira bist. Pert, p. 29.
The best sort of the officinal or Calabrian manna is in oblong pieces or flakes, moderately dry, friable, very light, of a whitish or pale yellow colour, and in some degree transparent: the inferiour kinds are moid, unctuous, and brown. Both sorts are said to be sometimes counterfeited by compositions of sugar, honey, and purgative materials; compositions of this kind, in a solid or dry form, may be distin-guished by their weight, compactness, and un-transparency: both the dry and moist compositions may be distinguished by their taste, which is sensibly different from that of true manna, and with greater certainty by their habitude to menstrua.
This juice liquesies in a moist air, dissolves readily in water, and, by the assistance of heat, in rectified spirit also; the impurities only being left by both menfsrua. On infpiffating the watery solution, the manna is recovered of a much darker colour than at first. From the saturated spirituous solution, great part of it se-parates as the liquor cools, concreting into a flaky mass, of a snowy whiteness, and a very grateful sweetness: the liquor, remaining after the separation of this pure sweet part of the manna, leaves, on being infpiffated, an unctuous, dark coloured, disagreeable matter, in greater or less quantity according as the manna made use of was less or more pure.
Manna, in doses of an ounce and upwards, proves a gentle laxative: it operates in general with great mildness, so as to be safely given in inflammatory or acute distempers, where the stimulating purgatives have no place. It is particularly proper in stomachic coughs, or those which have their origin in the stomach; the manna, by its sweetness and unctuosity, contributing to obtund as well as to evacuate the offending humours: in this intention it is sometimes made into a linctus or lohoch, with equal quantities of oil of almonds and of syrup of violets. In some constitutions, however, it acts unkindly, especially if given in considerable quantity, occasioning flatulencies, gripes, and dis-tenfions of the belly; inconveniences which may be generally obviated by a small addition of some grateful aromatic. It does not produce the full effect of a cathartic, unless taken in large doses, as two ounces or more, and hence is rarely employed in this intention by itself: it may be commodiously dissolved in the purging mineral waters, or acuated with the cathartic salts, or other purgatives; its efficacy is said to be peculiarly promoted by cafia sistularis, a mixture of the two purging more than both of them separately. See Cafia.