B. Lichens as Medicine
a. Ancient Remedies. An interesting note has been published by Müller-Argau[1266] which seems to trace back the medicinal use of lichens to a very remote age. He tells us that Dr Schweinfurth, the distinguished traveller, who made a journey through the valley of the Nile in 1864, sent to him from Cairo a piece of lichen thallus found in a vase along with berries of Juniperus excelsa and of Sapindus, with some other undetermined seeds. The vase dated from the 18th Dynasty (1700 to 1600 B.C.), and the plants contained in it must thus have lain undisturbed over 3000 years. The broken pieces of the lichen thallus were fairly well preserved; they were extremely soft and yellowish-white and almost entirely decorticate, but on the under surfaces there remained a few black patches, which, on microscopical examination, enabled Müller to identify them as scraps of Evernia furfuracea. This lichen does not grow in Egypt, but it is still sold there along with Cetraria islandica and some other lichens as foreign drugs. Dr Schweinfurth considered his discovery important as proving the use of foreign remedies by the ancient Egyptians.
b. Doctrine of “Signatures.” In the fifteenth century A.D. there was in the study and treatment of disease a constant attempt to follow the guidance of nature. It was believed that Providence had scattered here and there on plants “signatures,” or resemblances more or less vague to parts of the human body, or to the diseases to which man is subject, thus indicating the appropriate specific.
Fig. 131. Parmelia saxatilis Ach. (S. H., Photo.).
Lichens among other plants in which any “signature” could be detected or imagined were therefore constantly prescribed: the long filaments of Usnea barbata were used to strengthen the hair; Lobaria pulmonaria, the true lung-wort, with its pitted reticulate surface ([Fig. 72]), was marked as a suitable remedy for lung troubles; Xanthoria parietina being a yellow lichen was supposed to cure jaundice, and Peltigera aphthosa, the thallus of which is dotted with small wart-like tubercles[1267], was recommended for children who suffered from the “thrush” eruption.
The doctrine reached the height of absurdity in the extravagant value set on a lichen found growing on human skulls, “Muscus cranii humani” or “Muscus ex cranio humano.” There are a number of lichens that grow indifferently on a variety of substances, and not infrequently on bones lying in the open. This skull lichen[1268], Parmelia saxatilis ([Fig. 131]) or some other, was supposed to be worth its weight in gold as a cure for epilepsy. Parkinson[1269] tells us in all confidence “it groweth upon the bare scalps of men and women that have lyen long ... in former times much accounted of because it is rare and hardly gotten, but in our own times much more set by, to make the ‘Unguentum Sympatheticum’ which cureth wounds without the local application of salves ... but as Crollius hath it, it should be taken from the sculls of those that have been hanged or executed for offences.” Ray[1270] says that the same gruesome plant “is celebrated by several authors as useful in haemorrhages and is said to be an ingredient of the famous ‘Unguentum Armarium[1271],’ reported to have been invented by Paracelsus.” Another lost ointment!
c. Cure for Hydrophobia. Still another lichen to which extraordinary virtue was ascribed, was the very common ground species Peltigera canina ([Fig. 54]), a preparation of which was used in the cure of rabies. Dillenius[1272] has published in full the prescription as “A certain Cure for the Bite of a Mad Dog” which was given to him by a very celebrated physician of that day, Dr Richard Mead, who had found it effective:
“Let the patient be blooded at the arm, nine or ten ounces. Take of the herb called in Latin Lichen cinereus terrestris, in English Ash-coloured ground liverwort, clean’d, dry’d and powder’d half an ounce. Of black pepper powder’d two drachms.
“Mix these well together and divide the Powder into four Doses, one of which must be taken every Morning, fasting, for four Mornings successively in half a Pint of Cow’s Milk warm. After these four Doses are taken, the Patient must go into the cold bath, or a cold Spring or River, every Morning fasting, for a Month. He must be dipt all over but not stay in (with his head above water) longer than half a minute, if the Water be very cold. After this he must go in three Times a Week for a Fortnight longer.”
Lightfoot[1273], some forty years later, refers to this medicine as “the once celebrated ‘Pulvis antilyssus,’ much recommended by the great Dr Mead.” He adds that “it is much to be lamented that the success of this medicine has not always answered the expectation. There are instances where the application has not prevented the Hydrophobia, and it is very uncertain whether it has been at all instrumental in keeping off that disorder.” Belief in the efficacy of the powder died out before the end of the century but the echo of the famous remedy remains in the name Peltigera canina, the dog lichen.
d. Popular Remedies. Lichens with very few exceptions are non-poisonous plants. They owed their repute as curative herbs to the presence in the thallus of lichenin and of some bitter or astringent substances, which, in various ailments, proved of real service to the patient, though they have now been discarded in favour of more effective drugs. Some of them, on account of their bitter taste, were frequently used as tonics to replace quinine in attacks of fever. Several species of Pertusaria, such as the bitter P. amara ([Fig. 132]), and of Cladonia as well as Cetraria islandica ([Fig. 128]), were recommended in cases of intermittent fever; species of Usnea and others, as for instance Evernia furfuracea, were used as astringents in haemorrhages; others were given for coughs, Cladonia pyxidata ([Fig. 69]) being supposed to be specially valuable in whooping cough.
Fig. 132. Pertusaria amara Nyl. on bark (S. H., Photo.).
One of the most frequently prescribed lichens was the tree lung-wort (Lobaria pulmonaria) ([Fig. 72]). It was first included among medical plants by Dorstenius[1274], a Professor at Marburg; he gives a good figure and supplies directions for its preparation as a cure for chest complaints. The doctrine of “signatures” influenced practitioners in its favour, but it contains lichenin which acts as an emollient. In England, it was taken up by the famous Dr Culpepper[1275], who, however, believed in astrology even more than in signatures. He says: “it is of great use with many physicians to help the diseases of the lungs and for coughs, wheesings and shortness of breath which it cureth both in man and beast.” He adds that “Jupiter seems to own the herb.” A century later we find Dr John Hill[1276], who was a physician as well as a naturalist, stating that the great tree lung-wort has been at all times famous in diseases of the breast and lungs, but by that time “it was not much used owing to change in fashions.”
The only lichen that has stood the test of time and experience as a real remedy is Cetraria islandica, and even the “Iceland moss” is now rarely prescribed. The first mention in literature of this famous plant occurs in Cordus[1277] as the Muscus with crisp leaves. Some years later it figures among the medicinal plants in Sibbald’s[1278] Chronicle of the Scottish Flora, and Ray[1279] wrote of it about the same time as being known for its curative and alimentary properties. It was Linnaeus[1280], and later Scopoli[1281], who gave it the important place it held so long in medicine. It has been used with advantage in many chronic affections as an emollient and tonic. Cramer[1282] in a lengthy dissertation gathered together the facts pertaining to its use as a food, a medicine and for dyeing, and he gives recipes he had himself prescribed with marked success in many different maladies. It has been said that if “Iceland moss” accomplished all the good it was alleged to do, it was indeed a “Divine gift to man.”
The physiological action of cetrarin (acid principle of the lichen) on living creatures has been studied by Kobert[1283] and his pupils. It has not any poisonous effect when injected into the blood, nor does it work any harm when taken into the stomach even of small animals, so that it may be safely given to the most delicate patients. Nearly always after small doses peristaltic movements in the intestines are induced which indicate that as a drug it might be of service in the case of enfeebled organs. In larger doses it may cause collapse in animals, but if administered as free cetraric acid it passes through the stomach unchanged to become slowly and completely dissolved in the intestine. The mucous membrane of the intestine of animals that had been treated with an overdose, was found to be richer in blood so that it seems as if cetrarin might be of service in chlorosis and in assisting digestion.
Cetrarin has also been proved to be a nerve excitant which might be used with advantage in mental maladies.