Liverwort: a kind of imperfect vegetable production, consisting of spreading leaves, of a leathery crustaceous matter. A sort of flowers both male and female have been disco-vered in it, the latter producing innumerable seeds, like meal.

Lichen terrestris cinereus Rati. Lichen cani-nus Linn. Ash-coloured ground liverwort; consisting of roundish pretty thick leaves, divided about the edges into obtuse segments, flat above, of a reticular texture underneath, saf-tened to the earth by small fibres; when in perfection, of an ash grey colour; by age turning darker coloured or reddish. It grows on commons and open heaths, spreads quickly on the ground, and is to be met with at all times of the year, but is supposed to be in its greatest vigour about the end of autumn.

This herb is said to be a warm diuretic. It is particularly celebrated as a preservative against the terrible consequences of the bite of a mad dog: an account of the remarkable efficacy, in this intention, of a powder composed of the dry leaves and black pepper, was communicated to the royal society by Mr. Dampier, and published in No. 237 of the Philosophical Transactions. This powder was afterwards inserted, in the year 1721, into the London pharmacopoeia, at the desire of Dr. Mead, who had large experience of its good effects, and who declares, that he had never known it to fail, where it had been used, with the assistance of cold bathing, before the hydrophobia began. He directs a dram and a half of the powder to be taken in the morning fasting, in half a pint of cows milk warm, for four mornings suc-ceffively: previously to these four doses, the patient is to be blooded nine or ten ounces; and after them, to be dipt in cold water every morning falling for a month, and then dipt thrice a week for a fortnight longer (a). The powder was originally composed of equal parts of the lichen and pepper: but this quantity of pepper rendering the medicine too hot, only one part was afterwards used to two of the lichen. It is now expunged.

(a) Mechanical account ofpoisons, essay iii..

If cold bathing, bleeding, black pepper, and lichen, conjointly, be really of sufficient efficacy against the poison of the mad dog, it will not perhaps follow that any share of this efficacy belongs to the lichen: and indeed greater stress has been laid in general on the cold bath, than on this or the other parts of the prescription. The lichen doesnot promise to have any valuable medicinal power: to the organs of tasle or smell it discovers no activity: taken by itself, in double the quantity above prescribed, it did not appear to have any sen-sible operation. Digested in rectified spirit, it tinged the menstruumof a deep yellowish green colour: on distilling off the spirit from the siltered tincture, the remaining grumous extract had very little tafte, and amounted only to twenty-six grains from two ounces, or about one thirty-seventh of the weight of the lichen. A decoction of the herb in water was brownish, and of a faint smell, somewhat like that of mushrooms: the extract, obtained by infpiffating it, weighed one eighth of the lichen, and had some taste, but so little, that it is hard to say of what kind.

* Lichen islandicus Linn. Lichen Pharm. Edinb. Lichen terrestris, foliis Eryngii, Buxb. Cent. II. Lichenoides rigidum, Eryngii folia referent. Rail & Dillen. Eryngo-leaved, or eatable Iceland, liverwort. This species of lichen consists of nearly erect leaves, stiff when dry, but soft and pliant when moist, irregularly divided into broad distant segments, smooth, and ciliated at the margins. It grows in the mountainous parts of this country, and in various other parts of Europe.

The Iceland lichen infused in water gives a bitterish liquor, which is reddened by a mixture of martial vitriol. A decoction of it is very thick and viscid; and on cooling concretes into a strong gelly. An ounce of the lichen boiled for a quarter of an hour in a pound of water, and afterwards drained, yielded seven ounces of a mucilage as thick as that procured by the solution of one part of gum-arabic in three of water.

The inhabitants of Iceland make great use of this lichen both as food and as physic. When fresh, according to Borrichius (a), it is employed as a purgative; but Olafsen (b) denies that it has any more than a very gently opening quality. It is usually dried and ground into a meal, with which they make pottage and other preparations, adding either water or milk, and find it an agreeable and very nutritive article of food. It is best first to steep it for a sufficient time in water, in order to extract the bitterness.

The prepared lichen has been much used of late, particularly at Vienna, as a remedy for consumptive diforders. The celebrated Scopoli (c) has published some cases of its successful exhibition in the phthisis; and other practitioners (d) have confirmed his account. It is used boiled in milk to a kind of pottage, of which the patient's diet is chiefly to consist. It is said to be antiseptic, easy of digestion, and remarkably nourishing. It is also recommended in other cases, where the stomach is so weak that common aliments are rejected. The Edinburgh college have received this lichen into their catalogue of simples.

(a) Bartholini Act. med. Hasn. 1671.

(b) 'Journey to Iceland.

(c) Annus 2, historico-natural. p. 114.

(d) Bergius, mat. mcd. 858.